An epidemic of serum hepatitis (hepatitis-associated antigen [HAA]-positive) among surgical house staff occurred at Albert Merritt Billings Hospital in the winter of 1971. Four surgeons, who had operated on a patient in whom HAA-positive serum hepatitis subsequently developed, were affected. Arthralgia or arthritis and rash were prominent clinical features of this outbreak. Reduced synovial fluid complement level and a synovial fluid that was HAA-positive were found in one of the surgeons. A detailed evaluation of the 75 medical and allied medical personnel who cared for this patient before, during, and after surgery uncovered no additional cases of hepatitis. We believe, therefore, that the serum hepatitis virus was transmitted to the surgeons while they were operating, most likely through tissue penetration by contaminated surgical instruments or materials.