Neonatal male BALB/c mice were injected with diethylstilbestrol (DES), estradiol benzoate (E2B), testosterone propionate (TP), progesterone or DES, in combination with E2B, TP or progesterone and examined in adulthood. Body weight was reduced in males exposed to DES, TP or DES + TP, while testicular weight was reduced in animals injected with DES, E2B, TP, DES + TP or DES + progesterone. Exposure to DES and/or E2B also produced reproductive tract abnormalities and concomitant progesterone exposure did not further affect this parameter. Concomitant DES did not further alter the reduced plasma luteinizing hormone (LH) levels attributable to neonatal TP or E2B treatment. Plasma follicle-stimulating hormone (FSH) levels in intact males were increased by DES, DES + progesterone or progesterone alone. Assessment of the feedback effects of exogenous gonadal steroids on pituitary gonadotropin release in castrated adults indicated that injection of 125 micrograms TP further increased the already elevated post-castration levels of LH and FSH in mice neonatally exposed to progesterone. The increase in testosterone (T) concentration after intratesticular human chorionic gonadotropin (hCG) administration was significantly attenuated in mice neonatally exposed to DES plus E2B or to progesterone. Basal testicular T levels were significantly elevated in males exposed to DES, alone, or in combination with progesterone. Exposure to DES and TP increased hypothalamic serotonin (5-HT) levels in intact mice, while levels of 5-HT were lower after castration compared to controls. DES + E2B-treated mice had higher norepinephrine (NE) levels, and E2B-treated mice also had higher 5-HT levels.(ABSTRACT TRUNCATED AT 250 WORDS)