Female Sprague-Dawley rats were provided with an adequate (25% casein) or low (6% casein) protein diet, fortified with methionine, starting 5 wk prior to gestation and continuing until the birth of their pups. At birth, the offspring were fostered to well-nourished lactating dams as follows: in Experiment 1, litters contained eight prenatally malnourished pups; in Experiment 2, litters consisted of four pups with prenatal malnutrition and four well-nourished pups; control litters for both experiments contained eight well-nourished pups. In Experiment 1, the time spent in passive nursing and pup grooming was significantly higher for dams rearing previously malnourished pups than for those rearing control litters. In Experiment 2, mixed litters were groomed less frequently than control litters, but there was no significant difference between groups for any other measure. In both experiments, the prenatally malnourished pups showed similar body weight deficits relative to well-nourished pups. These findings underscore the usefulness of mixed litters in studying the later effects of prenatal malnutrition because later deficits in brain function are less likely to be attributable to changes in the early rearing environment.