Developmental exposure to di(2-ethylhexyl) phthalate (DEHP) demasculinizes male rat offspring by reducing anogenital distance (AGD), causing nipple retention (NR), and malforma¬tions and weight reductions of some reproductive organs. We investigated the effects of perinatal DEHP exposure in part A and B from a study, in which time-mated Wistar rats were gavaged from gestation day 7 to postnatal day 16 with 0, 10, 30, 100, 300, 600 and 900 mg/kg bw/day and 0, 3, 10, 30 and 100 mg/kg/day, respectively. The dose levels were selected with the aim of covering the whole dose-response curve for the demasculinizing effects of DEHP as well as investigating low dose effects. Our results demonstrate that DEHP at a relatively low dose of 10 mg/kg causes adverse anti-androgenic effects on male rat development. At this dose level, male anogenital distance was decreased, the incidence of nipple retention was increased, weight of levator ani/bulbocavernosus muscle was reduced and mild external genitalia dysgenesis was observed. Higher doses of DEHP, i.e. from 100 mg/kg, additionally induced histopathological effects on the testes, reduced testicular and prostate weight, and reduced expres¬sion of androgen-regulated genes (PBP C3 and ODC mRNA) in the prostate. The results provide new evidence of low-dose effects of DEHP, supporting that the cautious NOAEL of 5 mg/kg for DEHP that has been decided in EU is appropriate. Our results also indicate a reason for concern about the current exposure level of the human population.