['The use of leukocyte-depleted platelet concentrates (PCs) is justified, yet questions remain regarding their properties. We have assessed the in vitro quality of WBC-reduced PCs obtained by using a new in-line filter.', 'Twenty blood units were randomized for standard component preparation, or for processing including in-line leukodepletion of platelet-rich plasma using an ATS(TM) PL Pall filter. The resultant PCs were compared during storage for several in vitro platelet quality parameters, content of cytokines and anaphylatoxins, and coagulation markers.', 'In-line filtration of platelet-rich plasma through ATS PL was highly efficient rendering PCs with 99.93% less white blood cells (WBCs) than standard PCs. During storage for up to 9 days, leukocyte-depleted units displayed platelet content, biochemical parameters, and platelet surface expression of glycoproteins Ibalpha, IIb/IIa, CD62 and CD63, similar to those of standard units. However, in-line leukocyte-reduced PCs displayed no significant accumulation of IL-6 and IL-8 during storage in contrast to standard units. Moreover, while storage promoted complement activation with C3a and C4a liberation in both WBC-reduced PCs and standard units, the concentration of these anaphylatoxins after the 9-day storage period was higher in the former group. Finally, all units, standard and leukocyte-reduced, displayed a similar storage-promoted rise in TGF-beta(1), and a mild prolongation of activated partial thromboplastin and prothrombin times.'] Does evaluation of leukocyte-depleted platelet concentrate obtained by in-line filtration?