Recently, the leukocyte-derived cytokines interleukin (IL)-1 beta, IL-6, IL-8, and tumor necrosis factor(TNF)-alpha were found in considerable concentrations in platelet concentrates (PC) involved in nonhemolytic transfusion reactions (NHTR). We investigated transfusion reactions in two study periods over the last 3 years. In the 1st period, PC were leukocyte-depleted by bedside filtration. In the 2nd period we performed prestorage leukocyte filtration of PC. Recipients who experienced a transfusion reaction were tested for total and specific IgE, and reactions were analyzed with regard to the main symptoms. In the supernatant of platelets involved, we analyzed concentrations of IL-1 beta, IL-6, IL-8, TNF-alpha, macrophage inflammatory protein(MIP)-1 alpha, and RANTES. The incidence for NHTR did not change with the kind of PC transfused (n = 44, 1.63% and n = 46, 1.56%; p = 0.84), but allergic reactions were reduced in the 2nd observation period (0.92% versus 0.51%; p = 0.02). IL-1 beta, IL-6, IL-8, TNF-alpha, and MIP-1 alpha were not detectable in the majority of all products. PC involved in allergic reactions contained significantly higher concentrations of RANTES. We found evidence that the proinflammatory chemokine RANTES, stored in the platelet alpha-granules, is involved in allergic transfusion reactions. In contrast, leukocyte-derived inflammatory cytokines were of minor relevance in the onset of NHTR.