The effect of a high linoleic acid diet on blood pressure, renal function, and urinary prostaglandin excretion was studied in rats with decreased renal mass. Subtotally nephrectomized (5/6 nephrectomy) male rats received either a 15% linoleic acid (high linoleic acid, HLA) diet containing 20% safflower oil or a 0.28% linoleic acid (low linoleic acid, LLA) diet containing 20% coconut oil. Sham-operated rats were also placed on either HLA or LLA diet. The subtotal nephrectomized rats developed similar degrees of hypertension during the first 3 weeks after subtotal nephrectomy. However, 4 weeks after subtotal nephrectomy, the rats on HLA diet had significantly lower blood pressure than the rats on LLA diet [HLA 152 +/- 3 (mean +/- SE) mm Hg versus LLA 171 +/- 3 mm Hg]. This difference persisted until termination of the experiment at 7 weeks after subtotal nephrectomy (HLA 159 +/- 7 mm Hg versus LLA 192 +/- 6 mm Hg). The GFR measured 7 weeks after subtotal nephrectomy was significantly lower in both of the subtotally nephrectomized groups. However, the HLA subtotal nephrectomized rats had significantly higher GFR than the LLA-treated rats (HLA 0.23 +/- 0.05 ml/min 100 g versus LLA 0.12 +/- 0.02 ml/min/100 g, P less than 0.05). There was no difference in the GFR or blood pressure in the sham-operated rats treated with HLA or LLA diet. PGE2 excretion was lower in the two groups of subnephrectomized rats, but there was no difference between the HLA and LLA treated rats. Urinary 6-ketoPGF1 alpha was not decreased by subtotal nephrectomy and there was no difference between the dietary groups. However, TXB2 excretion was higher in the groups with subtotal nephrectomy, but there was no difference between the two dietary groups. In conclusion, the HLA diet attenuates the rise in blood pressure after subtotal nephrectomy in the rat and preserves renal function. There was no difference in urinary excretion of PGE2, 6-keto-PFG1 alpha, or thromboxane B2 between the two dietary groups.