Paraffin-embedded tissue sections from 29 patients with primary liver carcinomas were retrospectively studied for the presence of estradiol and testosterone using the peroxidase-antiperoxidase (PAP) technique. Twenty-seven hepatomas and two cholangiomas were treated with antiestradiol and antitestosterone primary serum. Estradiol was detected in 17 cases and testosterone in 11 cases of hepatomas. The two cases of cholangiocarcinoma were positive for estradiol and negative for testosterone. The immunohistochemical reaction in the tumor cells was mainly cytoplasmic and in a few cases both cytoplasmic and intranuclear. The positivity of the reaction in the tumour cells was compared with that of the adjacent non-neoplastic liver tissue and bile duct cells. Our findings were also analyzed in relation to tumor differentiation and the age and sex of the patients.