Plasma concentrations of testosterone (T), follicle stimulating hormone (FSH), and luteinizing hormone (LH) and percent binding of T o t plasma protein (TB) were studied in 16 normal fertile men and in 81 men who had undergone vasectomy from 1 to 5 yr earlier. No significant difference from the control values to T = 582 ± 39.5 (SE) ng/100 ml; FSH = 15.09 ± 2.18 (SE) mlU/ml; LH = 10.03 ± 1.13 (SE) mlU/ml and TB = 92.99 ± 0.285 (SE) % binding was detected in any group of the vasectomized men in any of the parameters studied. (J Clin Endocrinol Metab40: 868, 1975)