Influence of CD-3400, which has been developed as a new antihypertensive agent in the class of rauwolfia alkaloids, was studied and effects were compared to those seen with reserpine. A single, oral administration of CD-3400 in a dose of 50 mg/kg to female rats had no effects on ovarian estradiol levels in contrast to the significant decrease at 6 and 18 hr seen after reserpine administration. CD-3400 given in a dose of 50 mg/kg to female rats increased to a lesser degree the adrenal corticosterone level at 1 hour than did reserpine. While the serum corticosterone level in the female rats was not changed with CD-3400 administration, a large increase was detected in the case of reserpine. Administration of CD-3400 or reserpine in a dose of 100 mg/kg to male rats produced no change in the testicular testosterone level, but in both cases induced a significant decrease in the testicular estradiol levels. This inhibition was higher in the case of reserpine treatment. In addition, the serum corticosterone level in male rats treated with reserpine was higher than levels after administration of CD-3400. Our results indicate that CD-3400 exerts a weaker effect than does reserpine on gonadal and adrenal functions of both sexes of rats.