Samples of platelet concentrate prepared by double plasmapheresis of volunteers were stored at 4 C and 22 C for four to ten days and cultured from 0072 hours on brain heart infusion media, thioglycolate broth, and tryptic soy broth and incubated at 22 and 37 C for 21 days. A closed system was used for 42 units and a limited entry system involving pooling of platelet concentrates was used for 68 units. All 110 units were negative for bacterial contamination at both 4 C and room temperature, based on cultures using multiple media under maximized growth conditions for anaerobic as well as aerobic bacteria. Platelet concentrates handled in both a closed system and a limited entry system and stored up to at least 72 hours at room temperature remained free of bacterial contamination and appeared safe for transfusion.