Adult female albino rats were treated with a combined gonadal preparation for 28 days to ascertain whether it interacted with ovarian steroidogenesis or intervened in the control GABAergic system to inhibit ovulation. Δ5-3β -hydroxysteroid dehydrogenase (Δ5-3β-HSD) activity was determined from ovary and adrenal glands from the decapitated animals. The concentration of γ-aminobutyric acid (GABA) was estimated from the intact and discrete areas of the brain. Ovarian Δ5-3β-HSD activity decreased and that of adrenals increased significantly compared to controls, while GABA concentration decreased significantly in the intact brain. GABA concentration decreased in the hypothalamus, striatum-hippocampus, and midbrain-thalamus-subthalamus and increased significantly in the cortex compared to control. The gonadal preparation suppresses steroidogenesis in the ovary and augment in the adrenals. It may therefore be postulated that the central neurotransmitter activity of GABA is involved in the regulation of gonadotrophin release.