Haemonetics V 50 (HV-50), Fenwal CS 3000 (FCS-3000) and IBM 2997 separators are compared according to the results of donor plateletaphereses. The mean platelet yield of HV-50, FCS-3000 and IBM-2997 was 464 X 10(9), 551 X 10(9) and 468 X 10(9) respectively (the difference both between FCS-3000 and HV-50 and between FCS-3000 and IBM-2997 being significant - p less than 0.01). The median leukocyte contamination of platelet concentrates was 0.3 X 10(9), 0.2 X 10(9) and 5.3 X 10(9) respectively (the difference between FCS-3000 and HV-50 being not significant). The separators are further compared on the basis of platelet concentrate volume, erythrocyte contamination of thromboconcentrates, processing time, donor and staff convenience, our experience concerning product reliability and service quality, and finally the price of both the separators and the disposables.