An androgen binding protein (ABP) has been demonstrated in testis and epididymis (caput, corpus, cauda) supernatants of sheep aged 50, 120 and 200 days. This protein has a high affinity for 5α‐dihydrotestosterone (Ka = 0.184 ± 0.023 × 109M‐1), an electrophoretic mobility (RF) of 0.52–0.56 on PAGE and a molecular weight of about 70 000 daltons. In 50 day‐old animals (infantile) ABP is only present in the testis (392 fmoles/mg protein) with no dihydrotestosterone binding detectable in the epididymis. This is the first evidence of production of ABP by the testis some time before initiation of spermatogenesis. In the 120 day‐old animals (prepubertal), ABP is observed both in testis (142 fmoles/mg) and epididymis: caput (90 fmoles/mg), corpus (41 fmoles/mg) and cauda (165 fmoles mg). In the 200 day‐old rams (postpubertal) testis ABP is less concentrated than in younger animals (22 fmoles/mg), but in the epididymis the levels of ABP are twice those encountered in 120 d