BACKGROUND Increases in the use of single-donor apheresis components have increased the need for platelet donors. In the United States, persons must weigh 110 pounds or more to qualify as blood donors, and the same weight limitation has been placed on apheresis donors. Because automated plateletpheresis with some instruments differs considerably from whole-blood donation with respect to the volume of blood removed from the donor, the feasibility of using persons weighing between 90 and 110 pounds as platelet donors was evaluated by the use of the CS-3000 blood cell separator. METHODS The study was performed using female subjects who met all usual donor requirements except for minimum weight. The standard platelet collection procedure of the instrument was used, except that the blood processing rate was manually selected so as to optimize the blood withdrawal and return rate in individuals. Vital signs were recorded before and after donation as were signs or symptoms of any type of donor reaction. RESULTS Twenty-six of 28 women completed the donation procedure; in two instances, collection was terminated prematurely because of an inability to maintain adequate venous access. An average of 4.5 x 10(11) platelets were collected during a mean donation time of 110 minutes. All donors tolerated the procedure well, and no serious adverse reactions were seen. Because of the administration of priming solution and anticoagulant during apheresis, there was a net positive fluid balance following the procedure, in spite of the removal of approximately 220 mL of platelet concentrate. CONCLUSIONS These preliminary studies suggest that 90- to 110-pound persons may serve as plateletpheresis donors. Additional studies are needed to more fully document the safety and efficacy of this approach. The use of lower-weight donors may significantly increase the number of persons available to provide single-donor platelet components.