This chapter reviews the evidence from epidemiologic studies and controlled clinical trials dealing with dietary fats and blood pressure. Trials studying the effect on blood pressure of n-3 polyunsaturated fatty acids from fish oil show a dose-response hypotensive effect that may be restricted to patients with atherosclerotic cardiovascular disease. However, fish oil is not a practical therapy for hypertension given the large dose required (10 capsules per day) for a small effect (3-4 mmHg). From numerous studies, it is clear that saturated and n-6 polyunsaturated fats have no effect on blood pressure. Monounsaturated fats also have no effect but fewer studies have examined this relation.