Exposure to phthalate esters during sexual differentiation disrupts testosterone and insulin-like three hormones resulting in malformations of androgen- and insulin-like three-dependent tissues. The current study was designed to test the hypothesis that gubernacular lesions would be more prevalent in the DEHP-treated (750 mg/kg/day, gestational days 14-18) Wistar male than in the SD rat offspring, whereas the SD rat would display a higher incidence of epididymal agenesis. As hypothesized, striking differences were seen in the incidences of epididymal (67% in SD versus 8% in Wistar) and gubernacular lesions (0% in SD versus 64% in Wistar) among the two strains. In addition, fetal androgen and insl3 mRNA levels differed among the strains. SD fetal males had higher insl3 mRNA and lower T levels than Wistar males. The ratio of insl3 mRNA to T differed among DEHP-treated SD and Wistar fetal males, indicating that the steroidogenic pathway was more affected in the SD strain than in the Wistar strain. Taken together, these results suggest that the different malformation profiles produced by in utero phthalate treatment arise, at least in part, from strain differences in fetal Leydig cell function and the manner in which these cells respond to DEHP treatment.