On the basis of a variety of evidence androgenic hormones are thought to exert modulatory effects on immune function. Because specific actions of these hormones are exerted through receptor-mediated mechanisms, we have examined the human thymus gland for the presence of specific high-affinity androgen receptors. Cytosolic extracts of whole human thymus were found to contain 6.5 (+/- 2.6) fmol of specific [3H]methyltrienolone binding per mg protein. The receptor sedimented at 8s on sucrose density gradient centrifugation analysis. Thymic fibroblast lines derived from these glands did not express sufficient receptor content to account for the findings in whole thymus cytosolic extracts. Purified thymocyte preparations (greater than 99.3% pure as assessed by flow cytometry with monoclonal anti-thymocyte marker OKT11) contained 3.34 (+/- 1.2) fmol receptor per mg cytosolic protein. Mature peripheral blood lymphocytes, human T cells obtained from thoracic duct drainage, and the human T cell line Jurkat were not found to contain these receptors. These studies demonstrate for the first time that a high affinity androgen receptor is present in maturing human thymocytes. A functional role for these receptors is suggested by dihydrotestosterone-mediated decreases in interleukin 2-like activity produced by cultured human thymocytes.