Sixty-one primiparous Sprague-Dawley female rats were fed an adequate diet containing 5% protein (experiment 1) or 8% protein (experiment 2) throughout gestation. Low dietary protein reduced individual pup birth weight in both experiments (P less than .01 in experiment 1 and P less than .10 in experiment 2) and drastically decreased early postnatal survival in experiment 1. Weaning weight of survivors was reduced by gestation protein deprivation in experiment 1 but no in experiment 2. Male and female progeny surviving to weaning in experiment 1 and randomly selected progeny from each maternal treatment in experiment 2 were caged individually and fed ad libitum and nutritionally adequate corn-soybean meal-type diet throughout the entire life span. Body weight were recorded monthly beginning in young adulthood and continuing until death. Life span (in days) was recorded for each rat. Mature body weight of male and female progeny of dams fed restricted protein during gestation was less in both experiments than that of offspring from dams fed an adequate diet (P less than .01).  There was no effect of prenatal nutrition on life span in either experiment, but females lived significantly longer than males in both experiments (p less than .05). It is concluded that maternal protein restriction during gestation of a magnitude large enough to reduce pup birth weight causes a significant reduction in mature body size of the progeny without affecting longevity in the rat.