Treatment of male rats with phenoxybenzamine hydrochloride (PBZ), 70 μg/100 g body weight for 5 weeks, caused infertility of the rats. This effect was fully reversible. Studies on the weights of the testes, Epididymides, and male accessory sex glands, revealed increased glandular weights (significantly in the testes, epididymides and seminal vesicles). The number of spermatozoa found in the epididymis and vas deferens was significantly increased in the treated rats. Thus, PBZ caused a temporary cessation of sperm transport and paralysis of the muscles of the accessory glands, leading to the absence of ejaculation. In proestrous females mated with treated rats, this caused pseudopregnancy. No changes were found in the sexual behavior of the treated male rats, which was also supported by the absence of changes in the testosterone levels in serum and in testicular tissue. We recommend the use of PBZ in clinical trials, using this well-known drug as the active material for a future contraceptive pill.