AbstractBy premedicating the donor with 60 mg prednisone in divided doses and processing more donor blood at higher flow rates than those specified by the manufacturer, one can obtain high yields of granulocytes and platelets (mean of 3.3 × 1010and 5.9 × 1011, respectively) with the Fenwal CS‐3000 blood cell separator. The steroid effect predominates over that of processing more blood. In the case of donors who are not stimulated by steroid, processing 10 L of donor blood at flow rates of 60 to 70 ml/minute results in a significantly improved yield of granulocytes (mean of 2.2 × 1010as opposed to 1.4 in the case of 7 L) and of platelets (6.1 × 1011versus 4.7). The concentrates contain about 50 to 60% less lymphocytes when donors are given steroid. With these modifications, the leukapheresis can still be accomplished in less than three hours and with minimal adverse effects on the d