BACKGROUND Rh antigens are not present on the platelet surface. However, platelet concentrates may contain enough RBCs to elicit an anti-D response. Thus, D status must be considered in platelet transfusion. In immunosuppressed patients, frequencies of D alloimmunization of up to 19 percent have been previously reported. METHODS Here a prospective study is reported in which 22 D- patients with hematologic disease received D+ platelet transfusions. Platelet concentrates were prepared from whole-blood donations according to the buffy coat method and were pooled before administration. The antibody screen test to detect anti-D was performed by LISS- IAT using the gel test. RESULTS Our series comprises 22 immunosuppressed D+ patients with a median age of 56 years (range, 23-79). The patients received 121 D-incompatible pooled platelet transfusions. The mean +/- SD of RBC content was 4.17 +/- 1.74 mL. None of the 22 patients developed detectable anti-D after a median follow-up of 8 weeks (range, 1-37). CONCLUSIONS The risk of D alloimmunization is low in patients with hematologic disease after D-incompatible platelet transfusions using platelet concentrates prepared by the buffy coat method.