We determined costs and benefits of a community donor plateletapheresis program (CDPP) designed to provide HLA-matched platelet transfusions for patients who were refractory to random-donor platelets (RDPs). Costs of establishing and maintaining the CDPP were $127,520 for the first year (1982). Benefits were expressed as cost savings attributed to the CDPP. After the program began, the use of RDP in the community was 17,458 units less than projected. Estimates of net cost savings during the first year ranged from $177,570 to $272,253 (1982 dollars; cost-to-benefit ratios were 1:1.39 to 1:2.14.) In a matched cohort study of marrow transplant patients, CDPP platelet transfusions were as effective as those from family donors while total platelet and red cell use was unchanged. In patients with acute leukemia treated with chemotherapy, significant reduction in both platelet and red cell use was seen after institution of CDPP support. We conclude that the CDPP is a cost-effective approach to platelet support.