Pregnant rat dams and offspring were exposed to a 5 or 2% soy lecithin preparation or a control diet. Enrichment was either lifelong beginning at gestation, limited to the time preceding, or the time following weaning, or absent (constituting a "pure" control group). The most marked early sensorimotor deficits (reflex righting and swimming development) were seen in the 5% soy lecithin preparation group, although all soy lecithin preparation-exposed offspring had elevated brain/body weight ratios and choline acetyltransferase levels. Later, animals exposed to lifelong 5 or 2% soy lecithin preparations were hypoactive, had poor postural reflexes, and showed attenuated morphine analgesia. The results indicate that dietary soy lecithin preparation enrichment during development leads to behavioral and neurochemical abnormalities in the exposed offspring.