Female rats with 1-3/4 nephrectomy were divided in two groups and pair fed for five weeks diets differing in their linoleic acid content. Five weeks after subtotal nephrectomy, values for glomerular filtration rate and renal plasma flow were significantly higher and the values of blood pressure significantly lower in rats fed a diet rich in linoleic acid. Systolic blood pressure averaged 156 ± 5.6 mm Hg in high and 215 ± 8.1 mm Hg in low linoleic acid-fed rats. Differences in the values of blood pressure between the two groups were observed three weeks after subtotal renal ablation and persisted throughout the period of observation. Inulin clearance averaged 0.89 ± 0.07 ml/min in the high and 0.44 ± 0.05 ml/min in the low linoleic acid group. Protein excretion in the urine was significantly less in rats fed the high linoleic acid diet (36.9 ± 4.4 mg/24 hr) than in those fed the low linoleic acid diet (90.1 ± 12.5 mg/24 hr). The weight of the remnant kidney five weeks after subtotal renal ablation was greater in rats fed a low linoleic acid diet as compared to those fed a high linoleic acid diet (P < 0.05). Glomerular lesions were more severe in rats fed a low linoleic acid diet than in those fed a high linoleic acid diet. Feeding high linoleic acid diets to normal and subtotally nephrectomized rats increased the content of linoleic and arachidonic acid in renal cortex and medulla. It is concluded that a diet with a high linoleic acid content improves renal function and prevents marked increases in blood pressure in rats with partial nephrectomy. The mechanisms responsible for this effect remain to be determined.