BACKGROUND: Trials of transfusions of platelets (PLTs) treated with amotosalen-based pathogen reduction (PR) showed lower corrected count increments (CCIs) compared to conventional PLT components (PCs). However, PR-PLTs and conventional PCs often differed in various factors besides PR. We compared transfusion efficacy of single-donor apheresis PCs treated with PR or gamma irradiation. STUDY DESIGN AND METHODS: Hematologic patients were assigned to receive PR-PLTs or gamma-irradiated conventional PCs, both prepared in PLT additive solution (PAS). One-hour CCI (primary endpoint), 24-hour CCI, time to next PLT transfusion, and transfusion requirement of red blood cells and plasma were analyzed. RESULTS: Forty-four patients assigned to PR-PLTs received 220 PR-PLTs and 136 conventional PCs; 72 controls received 517 conventional PCs. No differences between patient groups were observed for mean (±standard deviation [SD]) 1-hour CCI (11.4 [±4.9] for PR-PLT vs. 11.0 [±4.9] for controls), mean (±SD) 24-hour CCI (6.1 [±4.4] for PR-PLTs vs. 6.2 [±4.8] for controls), and for the other evaluated outcomes. No differences between PC types were observed for mean (±SD) 1-hour CCI (10.6 [±6.7] for PR-PLTs vs. 9.9 [±6.2] for conventional PCs) and mean 24 hour-CCI (3.3 [±3.9] for PR-PLTs vs. 4.2 [±5] for conventional PCs). Thirty-five percent of PR-PLTs and 38% of conventional PCs (p = 0.63) were associated with 1-hour CCIs of less than 7.5. Inadequate 24-hour CCIs were observed for 72% of PR-PLTs and 64% of conventional PCs (p = 0.002). CONCLUSIONS: Transfusion efficacy of single-donor apheresis PCs in PAS treated with amotosalen PR versus gamma irradiation is comparable.