Subcutaneous treatment of 50% EtOH extract of neem bark (Azadirachta indica A. juss) to male rats at the dose of 10 mg for 30 days caused arrest of spermatogenesis. The diameter of serminiferous tubule, Leydig cell nucleus and epithelial heights of epididymides were significantly reduced (p≤0.001). Sperm motility and density were significantly reduced. Reduced testicular and accessory organ protein, sialic acid and vesicular fructose content manifested arrest of spermatogenesis and depletion of androgen level.