Blood pressure and the rate of excretion of an oral salt load were examined in spontaneously hypertensive rats of the Okamoto strain after exposure in utero and during suckling to a high salt (3% NaCl, wt/wt), low salt (0.1%), control salt (0.8%), or high potassium (2.2% KCl, wt/wt) [corrected] maternal diet. After weaning, all offspring were given a diet containing 0.8% NaCl. There were small but significant differences in growth rate among offspring groups over the 60 weeks of observation, with rats exposed to perinatal low salt and high salt diet being lighter than those given control or high potassium diet. There were positive, significant correlations between body weight and blood pressure in all dietary groups at 8 weeks of age but not 16 or 24 weeks. Rats exposed to perinatal low salt diet had significantly lower blood pressures than the other three groups, which had similar blood pressures. Low salt rats also exhibited an exaggerated natriuresis after a single, oral salt load (0.15 M saline, 1% body weight) compared with the other three diet groups, which were not different from each other. High potassium rats had a reduced kaliuresis and diuresis after the salt load when compared with the other three groups. At 60 weeks of age, rats that received perinatal low salt diet had significantly heavier adrenal glands when compared with the other groups, and the high potassium group had significantly elevated plasma renin concentrations. Thus, maternal electrolyte intake during the perinatal phase may alter body fluid homeostasis in genetically susceptible individuals at maturity.