fig1 shows a catheter 100 for deploying stents in accordance with one embodiment of the invention . the catheter 100 has a distal end 108 and a proximal end 120 . the catheter 100 comprises a flexible tube 102 , which is connected to an inflatable balloon 104 proximate to its distal end . the balloon 104 is shown in the figure in its deflated state . a radio - opaque marker 18 is located on the balloon wall . the catheter 100 has at its distal end 108 a tapered tip 110 that may be inserted into a stenosis in order to open the stenosis . a syringe 130 maybe used to introduce a fluid into the tube 102 in order to inflate the balloon 104 as described in detail below . a longitudinal shaft 124 in the wall of the tube 102 is configured to receive a guidewire 126 used in navigating the catheter in the vascular system . a neck region 122 of the tube 102 intervenes between the distal end of the balloon 104 and the tip 110 . the proximal end of the tip 110 is broadened to form a shoulder at the distal end of the neck region 122 . a sliding positioner element in the form of an annular sliding ring 114 is mounted on the tube 102 proximal to the balloon 104 . the ring 114 is slidable along the tube 102 by means of a wire 116 that extends along the length of the tube 102 from the proximal end 120 of the catheter to the ring 114 . the sliding ring 114 and the wire 116 form a positioner for moving a stent from a position which it does not surround the balloon 104 to a position in which it surrounds the balloon 104 . fig2 shows the catheter 100 having a plurality of stents ( three are shown in fig2 ) 206 a , 206 b and 206 c , mounted on the tube 102 between the sliding ring 114 and the balloon 104 . the stents are separated from each other by separating rings 208 a and 208 b . the sliding ring 114 has been positioned so that the separating rings 208 a and 208 b and the stent 206 are contiguous with the balloon 104 . each stent 206 bears a radio - opaque markers 210 a , 210 b and 210 c . in use , the catheter 100 is introduced into the vascular system and navigated to a stenosis by methods well known in the art . fig3 shows the catheter 100 after having been navigated through the vascular system and positioned inside a blood vessel 202 . the balloon is located opposite a stenotic region 204 of the blood vessel 202 . the wire 116 is used to slide the sliding ring 114 distally along the tube 102 so as to push the stents 206 a , 206 b , 206 c , distally . the sliding ring 114 is pushed distally along the tube 102 so that the stent 206 a is pushed over and around the balloon 104 , which is thereby brought into the lumen of the stent 206 a , and the marker 118 on the balloon coincides with the marker 210 a of the stent , as determined for example by x - ray angiography . fig4 shows the stent 206 a surrounding the balloon 104 . a fluid is then introduced into the tube 102 . the fluid passes through the tube 102 and inflates the balloon 104 . it will be understood that the balloon may be inflated by other conventional means , as are known in the art . inflation of the balloon 104 expands the stent 206 a onto the stenotic region of the blood vessel 202 , as shown in fig5 . the fluid is then withdrawn from the tube 102 . withdrawal of the fluid from the tube 102 causes the balloon to deflate . after deflation of the balloon , the stent 206 a remains in situ in its expanded state . the catheter may then be navigated through the arterial system until the catheter is positioned with the balloon 104 at another stenotic region of a blood vessel . the sliding ring is pushed distally by the wire 116 so that the succeeding stent 206 b overlies the balloon 104 and the marker 118 coincides with the marker 210 b on the stent 206 b . the distal separating ring 208 a is pushed along the tube 102 , beyond the balloon 104 to the neck region 122 of the tube , where the separating rings are stored . the shoulder of the tip 110 retains the separating rings on the neck region . this process may be repeated until some or all of the stents 206 have been deployed . the catheter is then removed from the body . fig6 shows a catheter 600 for deploying stents in accordance with another embodiment of the invention . the embodiment of fig6 has many components in common with the embodiment of fig1 , and similar components are identified by the same reference numeral in both embodiments . the embodiment of fig6 has a cylindrical carriage 605 mounted on the tube 102 . the carriage has a plurality of annular depressions ( three are shown in fig6 ) 610 a , 610 b and 610 c configured to receive a stent as described below . the depressions 610 all have the same length a as indicated in fig6 , which is essentially equal to the length of the balloon 104 . between the depressions 610 are barriers 620 a and 620 b . the carriage 605 is made from an elastic material such as rubber . the carriage 605 is slidable along the tube 102 by means of a wire 116 that extends along the length of the tube 102 from the proximal end 120 of the catheter to the carriage 605 . the carriage 605 and the wire 116 form a positioner for moving a stent from a position in which it does not surround the balloon 104 to a position in which it surrounds the balloon 104 . fig7 shows the catheter 600 having a plurality of stents ( three are shown in fig7 ) 206 a , 206 b and 206 c mounted on the annular depressions of the tube 102 . the stents are separated from each other by the barriers 620 a and 620 b . in the present embodiment the stents are of different lengths . however , they may also be of the same length . each stent 206 bears a radio - opaque annular marker 210 a , 210 b and 210 c . the catheter 600 is introduced into the vascular system and navigated to a stenosis by methods well known in the art . fig8 shows the catheter 600 after having been navigated through the vascular system and positioned inside a blood vessel 202 . the balloon is located within a stenotic region 204 of the blood vessel 202 . the wire 116 is used to slide the cage 605 distally along the tube 102 so as to move the stents 206 distally . the carriage 605 is pushed distally along the tube 102 until the balloon 104 is brought into the lumen of the stent 206 a and the marker 118 on the tube coincides with the marker 210 a , as determined for example by x - ray angiography . in a similar manner , the balloon may be slid within the carriage until it is positioned opposite the stent . fig9 shows the stent 206 a surrounding the balloon 104 . a fluid is then introduced into the tube 102 . the fluid passes through the tube 102 and inflates the balloon 104 . inflation of the tube 104 expands the portion of the carriage 605 surrounding the balloon 104 which in turn expands the stent 206 a onto the stenotic region of the blood vessel 202 , as shown in fig1 . the fluid is then withdrawn from the tube 102 into the syringe 130 . withdrawal of the fluid from the tube 102 causes the balloon to deflate . after deflation of the balloon , the stent 206 a remains in its expanded state . the catheter is then navigated through the arterial system until the catheter is positioned with the balloon 104 in another stenotic region of a blood vessel . the catheter is then pushed distally by the wire 116 so that the stent 206 b overlies the balloon 104 and the marker 118 coincides with the marker 210 b on the stent 206 b . in this embodiment , the stents may be deployed in any order . this process may be repeated until some or all of the stents 206 have been deployed . the catheter is then removed from the body . this example illustrates an embodiment which is an improvement over the embodiment described in example i . with reference to fig1 , there is shown a catheter 700 having a distal end 108 and a proximal end 120 . as in fig1 , the catheter 700 comprises a flexible tube 102 , which is connected to an inflatable balloon 704 proximate to its distal end . a radio - opaque marker 118 is located on the balloon wall . the catheter 700 has at its distal end 108 a tapered tip 110 , but unlike in example i , there is no neck region , and the tip is not enlarged . the balloon in this embodiment may be a conventional inflatable balloon used in balloon angioplasty . as in example i , a guidewire 126 extends along the tube 102 , exiting at the distal end 108 of the catheter . an anterior positioner in the form of a perforated sphere 706 is fixed to the guidewire anterior to the balloon 704 , e . g . the guidewire passes through a bore channel extending through the sphere . the diameter of the sphere is slightly larger than the diameter of the retracted stents which are mounted on the catheter . the purpose of the sphere will be explained below . the catheter 700 has a sliding ring 114 ( being the posterior positioner ) and a plurality of stents ( three are shown in fig1 ) 206 a , 206 b and 206 c , mounted on the tube 102 between the sliding ring 114 and the balloon 704 . while the anterior stents are generally of the same length , the posterior stent may be longer or shorter . in the illustrated embodiment , the posterior stent 206 c is shorter than the other stents . each stent 206 bears at least one radio - opaque marker 210 a , 210 b and 210 c , respectively . the stents are separated by separating rings 708 a and 708 b which are of the same length as the anterior stents . an anterior ring 710 is positioned between the most anterior stent 206 a and the balloon 704 and protects the distal edge of the anterior stent . this anterior ring may be shorter than the separating rings . the operation of this embodiment may be understood with reference to fig1 . as in example i , the wire 116 is used to slide the sliding ring 114 distally along the tube 102 so as to push the stents 206 a , 206 b , 206 c , distally . the sphere 706 is distanced from the distal end 108 of the catheter by pushing the guidewire 126 , thus providing free guidewire 712 on which components of the catheter may be stored . in fig1 , it may be seen that the anterior ring 710 and the separating ring 708 a have been pushed beyond the balloon 704 and onto the free guidewire 712 . the anterior stent 206 a ( not shown ) has been expanded and deployed within the blood vessel wall , and the middle stent 206 b is mounted on the balloon 704 , ready to be expanded . the radio - opaque marker 210 b of the stent 206 b is positioned opposite the radio - opaque marker 118 of the balloon 704 . thus , this embodiment also differs from that of example i in having more room to store the separating rings . in addition , all of the mounted stents and rings may be moved distally and proximally by pulling and pushing the anterior and posterior positioners , being the sphere 706 and sliding ring 114 , respectively , so that the stents may be deployed in any order . this differs from example i where the stents were required to be deployed in the order in which they were placed on the catheter . fig1 shows the catheter after the 2 anterior stents 206 a and 206 b ( not shown ) have been deployed , and the anterior 710 and separating 708 a & amp ; 708 b rings are positioned on the free guidewire 712 between the sphere 706 and the balloon 704 . it may be seen that the separating rings have annular protrusions 714 protruding from their outer surface . the purpose of these protrusions is to protect the blood vessel inner wall from being injured by the stents as the catheter travels through the vessel . the posterior stent 206 c is mounted on the distal half of the balloon 704 , while the anterior portion of the sliding ring 114 envelops the proximal end of the balloon . thus , when the balloon is inflated , only the distal half expands ( since the sliding ring resists the pressure of the balloon ), expanding the stent 206 c and deploying it in the blood vessel .