Rats exposed perinatally to dietary commercial soy lecithin preparation (SLP) showed alterations in sensorimotor development and brain cell maturation. Latencies for righting responses (measured on postnatal Days 1-4) and negative qeotaxis (measured on postnatal Days 5-8) were shorter in the SLP treated animals. This pattern was accompanied by specific alterations in cerebellar development; biochemical markers for cellular maturation indicated a compression of the ontogenetic time course, as assessed by ornithine decarboxylase (ODC) activity, and levels of nucleic acids and proteins. In contrast, cellular development in the cerebral cortex indicated a generalized slowing of the time course of maturation and a deficit in the number of cells which persisted into adulthood. Behavioral abnormalities also did not disappear in adulthood, as morphine analgesia was markedly reduced in the SLP group. These results indicate that exposure of the fetus and neonate to dietary SLP during development leads to regionally specific alterations in brain cell maturation associated with disruption or behavioral patterns.