1. An examination was made of the effect of prenatal, high salt (5% w/w) and low salt (0.1% w/w) diet on the blood pressure and ability to excrete a salt load of mature spontaneously hypertensive rats (SHR) of the Okamoto strain maintained on normal salt (0.8% w/w) diet after weaning. 2. Prenatal high salt diet resulted in a significant exacerbation of the hypertension of 4 month old SHR when compared with animals given prenatal low salt diet. 3. Three month old SHR given prenatal, high salt diet exhibited a significantly reduced Na+ excretion following a single, oral salt load (150 mmol/l, 1% bodyweight) when compared with the low salt group. 4. Thus, prenatal, high salt diet may influence body fluid homeostasis in genetically susceptible individuals later in life.