The androgen receptors in biopsy specimens of 22 cases of human prostatic cancer (PC) were studied by radioligand binding assay. The cytoplasmic androgen receptor (AcR) and nuclear androgen receptor (AnR) densities were 305.70 +- 461.68 and 363.04 +- 391.44 pmol/g protein respectively, both were significantly higher than those of 36 benign prostatic hypertrophy (BPH) and 9 normal prostate (NP). Among the prostatic cancers, the AnR/AcR ratios were significantly different between metastatic and primary cancers. This result suggested that there might be migration of AR from nucleus to cytosol in the process of metastasis. The serum testosterone studied by RIA method are significantly lower than that of BPH and NP. Thawmounted autoradiography demonstrated that AR were mainly located in epithelial cells of the glandular tissue of prostate.