1. In a tamper-resistant package, at least one over sized closeable outer enclosure and at least one inner enclosure fitted with closure means containing at least one flowable material in addition to the product, and means associated with said package for making available higher pressure inside the inner enclosure than that of its surrounding atmosphere, space between said outer and inner enclosures contains a predetermined amount of flowable material suitable for the proper functioning of said package, the internal pressure in said outer enclosure is reduced to a predetermined level below that of its surrounding atmosphere by drawing out a suitable quantity of its flowable contents before closing it, the walls of said outer enclosure press against the walls of said inner enclosure which holds the product and restricts its movement therein to a predetermined extent, means associated with said package for manifesting evidence that tampering with said package has occurred in the event that the contents in said inner enclosure is tampered with through at least one aperture made in said walls of said package leading to the product therein.