Randomized studies testing the clinical efficacy of platelet additive solutions (PASs) for storage of platelets are scarce and often biased by patient selection. We conducted a multicenter, randomized study to investigate clinical efficacy of platelets stored in PAS II versus plasma, also including patients with clinical complications associated with increased platelet consumption. A total of 168 evaluable patients received pooled buffy coatderived platelet concentrates (PCs) suspended in either plasma (n ‫؍‬ 354) or PAS II (n ‫؍‬ 411) stored up to 5 days. Both univariate as well as multivariate analysis showed a significant effect of used storage medium in regard to 1-and 24-hour count increments and corrected count increments, in favor of plasma PCs. However, there were no significant differences between the groups regarding bleeding complications and transfusion interval. Adverse transfusion reactions occurred significantly less after transfusions with PAS II PCs (P ‫؍‬ .04). Multivariate analysis showed no significant effect of the used storage medium on the incidence of 1-and 24-hour transfusion failure. We showed safety and efficacy of PAS II PCs in intensively treated patients; however, plasma PCs show superior increments. (Blood. 2006;108:3210-3215)