The ambiguous influence of bendazol (5 and 160 mg/kg) on the sexual behavior and spermatogenesis of rats was observed in experiments on male rats. An increase in the duration of sexual activity and a decrease of the total amount of spermatozoons were registered irrespective of the course of drug administration in a dose of 5 mg/kg. In males treated with bendazol in a dose of 160 mg/kg, the behavior varied depending on the duration of treatment: the sexual activity decreased upon a 5-day treatment and increased after a 2-month course. The index of spermatogenesis did not depend on the time of administration at 5 or 160 mg/kg, while the spermatozoon mobility was suppressed upon the short-term treatment and increased upon the log-term administration of bendazol.