Five hundred seventy-six consecutive patients from the surgical, obstetrical, and medical services who had received transfusions of volunteer blood were followed-up at regular intervals for 6 mo. Fifty-three (9.2%) developed acute posttransfusion non A, non B hepatitis. Forty-seven (89%) had an incubation period between 2 and 8 wk. The frequency was not related to the age or sex of the patient, the indications for transfusion, the type of surgery, anesthesia, the presence of perioperative hypotension, or the number of units of blood transfused. There were no cases of fulminant hepatitis. Nineteen of the 53 patients (36%) with acute posttransfusion hepatitis progressed to chronic hepatitis. Development of chronic hepatitis was not related to the age or sex of the patient, the incubation period of the preceding acute hepatitis, the presence of shock or malignancy, or the number of units of blood transfused. Patients with higher levels of alanine aminotransferase during the acute hepatitis were more prone to develop chronic hepatitis. The finding of 9.2% of transfusion-related hepatitis in recipients of hepatitis B surface antigen-screened blood from volunteer donors underscores the potential sequelae of blood transfusion, especially as a source of contribution to the pool of chronic liver disease.