antirh1 antid alloimmunization after transfusion of platelet concentrates from rh 1 donors antierythrocyte alloimmunization may occur following the transfusion of platelet concentrates in response to the presence of residual erythrocytes immunization against rh1 d antigen is the most frequent but transfusion of rh1 compatible platelet concentrates is not always possible because of supply constraints we report here three cases of antirh1 antid alloimmunization in rh 1 patients after transfusion of platelet concentrates from rh 1 donors criteria for selection of platelet concentrates are numerous and difficult to achieve in practice respect of rh1 compatibility is not obligatory but in case of transfusion of rh1 incompatible platelet concentrates antirh1 immunoprophylaxis must be made for rh 1 women of childbearing age and without profound immunosuppression as recommended by afssaps agence franaise de scurit sanitaire des produits de sant these data point out the need to perform posttransfusional screening test for irregular erythrocyte antibodies as part of the transfusion of platelet concentrates