On d 7 or 12 of gestation or on d 2 postpartum, Swiss ICR dams were administered either (1) a single intragastrk dose of Pt(SO4) at the LD1 level or dilute H2O4at an equivalent volume, pH, and sulfate content, or (2) a single subcutaneous dose of Na, PtCl6or phosphate‐buffered saline at an equivalent volume and pH. To differentiate prenatal from postnatal effects of the compounds on the offspring, a full cross‐fostering design was employed. Rate of growth (as a function of weight gain) and gross activity of the neonates were assessed on d 8 or 13 postpartum. On d 60–65 postpartum, open‐field behavior (ambulations and rearings), rotarod performance, and passive avoidance learning of the adult offspring were investigated. Exposure to Pt(SO4)2resulted in reduced offspring weight from d 8 to 45 postpartum, whereas the major effect of Na2PtCl6was a reduction in activity level of the offspring of mothers exposed on d 12 of gestation.