The effect of the gamma isomer of 1,2,3,4,5,6-hexachlorocyclohexane (Y-HCH), lindane, on reproductive function in the female rat was examined in two experiments. In the first experiment, chronic treatment with 0, 5, 10, 20, and 40 mg/kg lindane delayed vaginal opening and disrupted ovarian cyclicity until approximately 110 days of age. Thereafter regular ovarian cycles were present in the majority of females in all dose groups. When sacrificed on the day of vaginal proestrus, the females receiving the two higher doses of lindane had smaller pituitary and uterine weights, lower serum and pituitary luteinizing hormone (LH) and prolactin and higher pituitary follicle stimulating hormone (FSH) concentrations than the oil-treated control females. In a second experiment, the uterine weight and pituitary hormone response to a 10 micro injection of estradiol benzoate (EB) to 28-day-old, lindane-treated females was investigated. The uterine weights of the lindane treated prepubertal females were significantly lower than controls at 30 hs after EB injection. Data indicate that lindane may effectively block the response of estrogen-dependent tissues to this ovarian steroid hormone and that this apparent antiestrogenic effect of lindane is responsible for the disturbances observed in the neuroendocrine control of ovarian function in the rat. (Copyright (c) 1989 by Academic Press, Inc.)