Stapling or suturing for anastomoses of the left side of the large intestine. Two hundred and fifty patients undergoing elective surgical treatment involving anastomoses of the left side of the colon or colon and rectum have been studied in a randomized trial in which the EEA (U. S. Surgical Corp.) circular stapler has been compared with single layer sutured anastomoses. Only patients in whom either technique was feasible were included in the analysis. The operative techniques were largely standardized. Patients were studied by means of a limited barium enema on the ninth or tenth postoperative day. The data have been analyzed for leakage rate (clinical and roentgenologic), other complications and degree of experience of the surgeon. Eleven patients were excluded from the analysis because the selected technique could not be carried out; of these, eight were in the stapled group in which it was possible to perform a sutured anastomosis. There were no instances in which it was possible to staple but not possible to suture. The remaining three exclusions were patients in whom either a coloanal anastomosis or a Hartmann procedure was performed. There was no over-all difference in the leakage rate--roentgenologic, clinical or total--between the two groups. However, when analyzed by the surgeon, the clinical leakage rate for surgeons in training was greater for sutured anastomoses than for stapled anastomoses (p = 0.053). Thus, it appears that the benefits of experience are more pronounced for sutured anastomoses but that, in experienced hands, neither technique is superior. 