Transient pure red-cell aplasia is a rare complication of persistent acute hepatitis. We have investigated possible mechanisms for marrow suppression in one such patient who developed erythroid aplasia in the course of transfusion-related hepatitis. The patient's lymphocytes, obtained during the acute illness, markedly inhibited erythroid colony formation by donor marrow. After the patient recovered, remission lymphocytes in co-culture did not inhibit colony formation. No reversible suppression was demonstrable by addition of patient serum. These observations suggest that hematocytopenias associated with hepatitis may result from cell-mediated suppression induced by hepatic injury.