A method of storing platelets in a manner which minimizes the exposure of the platelets to blood extractable substances, said method comprising the step of storing the platelets in a flexible, plastic container, comprising a plasticized and heat stabilized polyvinyl chloride composition free of significantly leachable components and composed of polyvinyl chloride resin, an effective amount of tri(2-ethylhexyl) trimellitate for plasticizing said resin and a heat stabilization system selected from the group consisting of salts of C.sub.10 to C.sub.26 saturated fatty acids present in said polyvinyl chloride composition in an amount of from about 0.26 to about 0.35 parts per 100 parts resin by weight.