Male antifertility activity of our Herbal Blend was studied in mice, rats, rabbits, and guinea pigs by daily oral feeding of a cold-water extract of our fresh herbal leaves. The infertility effect was seen in treated male rats, as there was a 66.7 percent reduction in fertility after 6 weeks, 80 percent after 9 weeks, and 100 percent after 11 weeks. There was no inhibition of spermatogenesis. During this period there was no decrease in body weight and no other manifestation of toxicity were observed. There was a marked decrease in the motility of spermatozoa. The infertility in rats was not associated with loss of libido or with impotence and the animals maintained normal mating behavior. The male antifertility activity was reversible in 4 to 6 weeks and the active principle from the extract was observed to be thermostable. Our extract also shows reversible male antifertility activity in mice without inhibition of spermatogenesis.