The effects of neonatal diethylstilbestrol (DES) exposure on the volume of the sexually dimorphic nucleus of the preoptic area of the hypothalamus (SDN-POA) and on GnRH-stimulated LH secretion were investigated in castrated female rats of known anogenital distance (AGD) at birth. The AGD was measured in females on the day of birth, and 0.1 microgram DES or corn oil was injected from Days 1 through 10 of life. The volume of the SDN-POA was significantly larger in animals that had received DES than in those that had received corn oil. The largest SDN-POA volumes were seen in DES-treated animals that had long (> 1.4 mm) AGDs, and smallest volumes in corn oil-treated females that had short (< or = to 1.4 mm) AGDs. Within treatment groups, animals with longer AGDs had significantly larger SDN-POA volumes than those with short AGDs. Within AGD subgroups, the effect of DES was similar in that the percentage increase in SDN-POA volume was equivalent. Pituitary responsiveness to GnRH was greater in corn oil-treated females with long AGD than in similarly treated females with short AGD. DES treatment blunted LH secretion in both AGD subgroups, but the increased LH secretion was preserved in rats with long AGD. The results indicate that the individual effects of the postnatal environment depend on the androgenicity of the intrauterine microenvironment. Further, variations in the individual's response to potential environmental hazards may be predicted by antecedent intrauterine events.