The large-scale use of frozen red cells and washed red cells in this transfusion service has not been effective in reducing post-transfusion hepatitis. Seventy-eight per cent of 31,125 transfusions, excluding platelets and plasma, were given in the form of frozen or washed red cells. These transfusions were associated with 56 cases of hepatitis. In 37 cases, the recipients had received only frozen or washed red cells (or both). Post-transfusion hepatitis was of the non-A, non-B type in 95% of cases. On average, commercial blood accounted for 30 per cent of the donor base during the first four years and was involved in 44 of the 56 cases. Elimination of commercial blood from the donor base resulted in a decrease in the incidence of hepatitis from 2.1 to 0.3 per 1000 transfusions.