['A photochemical process has been tested for the inactivation of viruses and bacteria in buffy-coat derived platelet concentrates (BC PCs).', 'BC PCs in 35% CPD plasma and 65% platelet-additive solution (PAS III) were exposed to photochemical treatment (PCT) with 150 microM of the psoralen S-59 and a 3 J/cm(2) treatment with long-wavelength ultraviolet light (UVA, 320-400 nm). Platelet function was evaluated following PCT using a panel of in vitro assays.', 'This PCT process was highly effective at inactivating gram-positive bacteria (Staphylococcus epidermidis, Staphylococcus aureus, Enterococcus faecalis) and gram-negative bacteria (Enterobacter aerogenes, Pseudomonas aeruginosa, Serratia marcescens). No viable bacteria were detected following PCT and 7 days of platelet storage while bacterial growth was detected in paired untreated control BC PCs. Complete inactivation of the gram-positive Bacillus cereus was achieved only in one of two replicate experiments with BC PCs. PCT was also highly effective for inactivation of human immunodeficiency virus HIV-1 in BC PCs inoculated with approximately 10(6) tissue culture infectious doses per milliliter (TCID(50)/ml) of cell-associated HIV-1. Rapid inactivation was observed with increasing UVA doses: with 150 microM S-59 and a 1 J/cm(2) treatment of UVA, a reduction of 5.6+/-0.5 log TCID(50)/ml was achieved, and a reduction of >6.4 log TCID(50)/ml was achieved with 150 microM S-59 and a 3 J/cm(2) treatment of UVA. No physiologically relevant differences in platelet functions were found between the test and the control BC PCs during 7 days of storage.'] Does photochemical inactivation of bacteria and HIV in buffy-coat-derived platelet concentrate under conditions that preserve in vitro platelet function?