The separate and combined effects of protein deprivation and nitrofen exposure were studied in the pregnant rat. Animals were fed diets containing 24, 8, 6 or 4% casein throughout gestation. Within each diet group, sub-groups were gavage-fed with 12.5 (lower dose) and 25 (higher dose) mg nitrofen/kg body weight or with oil carrier only on days 7-21 of gestation. Dams were weighed and food intake was measured daily. On day 21 of gestation, cesarean-derived pups were examined for congenital anomalies and dissected for determination of organ weights. Skeletons were alizarin stained and examined for skeletal anomalies and developmental stage. No effects on the skeleton or gross congenital anomalies were seen. Fetal, size and weights of liver, kidney, intestine, heart, lung and brain were reduced with decreasing casein content of the diet and as a result of the higher dose of nitrofen.