Androgen receptors (AR) were assayed for cirrhotic liver, adenomatous hyperplastic nodule (AHN), and hepatocellular carcinoma (HCC) which were removed by partial hepatic resection from five patients. There were three men and two women. Age ranged from 59 to 68 years. Underlying cirrhosis was macronodular in three and micronodular in two. AHN was present within HCC in two patients, but these two lesions were found in different lobes of the same liver in another two patients. Only AHN was seen in the last patient. ARs in the cytosol of cirrhotic liver ranged from nil to 12.8 fmol/mg of protein with the dissociation constant (Kd) of 3.2-20.3 x 10(-10) M. AHNs possessed ARs ranging from 4.0 to 27.6 fmol/mg of protein (Kd values, 7.4-21.0 x 10(-10) M. All HCC nodules had ARs ranging from 11.8 to 72.8 fml/mg of protein with Kd values of 5.3-27.1 x 10(-10) M. Thus, cytosolic AR concentrations were highest in HCC, lowest in cirrhotic liver, and intermediate in AHN. The present study seems to indicate that AHN may be a precancerous lesion and that androgen and its receptor play an important role in human hepatocarcinogenesis.