Six patients with hepatitis B surface antigen-positive (HBsAg-pos) chronic liver disease have been treated with transfer factor (TF) prepared from leucocytes of normal blood donors with no history of hepatitis, and with TF from subjects recently recovered from type B hepatitis. In three patients there were transient elevations of aspartate transaminase (AsT) after 'specific' TF, representing damage or destruction of hepatocytes, and in two of these patients there was coincidental complement consumption, suggesting that TF had stimulated production of antibody. In one other patient there was an increase in E-rosetting lymphocyte (ERL) concentration representing a change in T-lymphocyte reactivity. One of the two patients who had no measured response to TF had a primary liver cell carcinoma and was receiving prednisolone therapy. TF prepared from subjects who have recently recovered from type B hepatitis may have temporarily altered the immunological status of patients with HBsAg-pos chronic liver disease, but it did not have a beneficial therapeutic effect.