17 out of 175 cases of early syphilis had clinical, biochemical, and immunological evidence of liver damage. Before penicillin therapy the histological appearance of the liver was abnormal in 14 of the 15 patients from whom biopsy specimens were obtained. In 7 cases, treponemes were seen in the liver. After two months' penicillin therapy the extent and severity of the histological abnormality was reduced. In the repeat liver-biopsy specimens obtained after penicillin treatment no treponemes could be demonstrated. It is suggested that the hepatitis found in these 17 cases of early syphilis was produced by treponemes.