Perinatal exposure to delta 9-THC has been shown to produce effects on brain development. In this study we evaluated the changes induced by maternal exposure to delta 9-THC (5 mg/kg per day) from gestational day 5 to postnatal day 24 in eight discrete brain areas on the central serotoninergic system in both adult male and female rats. These result show that maternal exposure to delta 9-THC from gestational day 5 to postnatal day 24 affects development of the various central indoleaminergic system of the offsprings brain. Perinatal exposure to delta 9-THC decreased the levels of 5-HT in hypothalamus and rostral neostriatum in exposed males, and also decreased the levels of 5-HT in ventral hippocampus, septum, and midbrain raphe nuclei in both exposed males and females. Perinatal exposure to delta 9-THC increased the levels of 5-HIAA in dorsal hippocampus, hypothalamus, septum, midbrain raphe nuclei, and rostral neostriatum in exposed males and females. We have also found differences between nonexposed males and females in several brain regions. Our results confirm a regional and sexual specificity in endogenous levels of indoleamine after perinatal delta 9-THC treatment, being the midbrain raphe nuclei the most affected area.