The association between maternal nutrition, fetal growth and the later development of hypertension was investigated in the rat. Animals were habituated to diets containing 18% (control) or 9% (low) protein by weight. The rats were mated and maintained on the diets until the end of pregnancy. Lactating dams were transferred onto standard chow diet. Systolic blood pressure was determined in male and female weanling offspring, using an indirect tail-cuff method. To assess the direct effects of low protein diets upon blood pressure of adult animals, a group of male and female rats were fed 18% or 9% protein for 14 days. Blood pressure was determined at the beginning and end of the feeding period. Blood pressure was additionally assessed over 14 days in pregnant rats fed control or low protein diets. Low protein diets did not alter systolic blood pressure in adult male or female rats. The blood pressures of pregnant females fed 18% or 9% protein diets did not significantly differ at any stage of pregnancy. Rats fed 9% protein diets gave birth to significantly smaller pups. Litter sizes were unaltered, and no differences in perinatal mortality were observed. Pups exposed to maternal low protein in utero had higher systolic blood pressure at the age of 4 weeks, when compared to control pups. The phenomenon was observed in both male and female offspring. Blood pressures at 4 weeks of age were strongly associated with maternal protein intake (r = -0.55). Associations were also noted between blood pressure and maternal weight at mating (r = 0.48), and weight gain in pregnancy (r = -0.30). Fetal exposure to maternal low protein diets induces hypertension in rats. The phenomenon is observed early in life and is independent of sex and the influence of maternal blood pressure. The low protein diet itself did not produce an increase in the blood pressure of adult rats.