In an experiment on 95 Wistar rats weighing 330 g the effect was studied of partially hydrogenated marine oil and cod-liver oil as well as sunflowerseed oil and animal fat on arterial hypertension induced with administration of 1.5% NaCl in drinking water. During 5 weeks the animals received diets containing 37.8 kcal% derived from the studied fats. After the first week of 1.5% NaCl solution administration a significant rise of the systolic blood pressure and heart rate was observed in all animals without regard to the fat received by them with the diet. The rise of the blood pressure was greatest in the group of rats kept on the diet with animal fat, while in the groups of rats receiving diets with sunflowerseed oil or marine oils this rise was significantly smaller, especially with cod-liver oil. The hypotensive effect of marine oils, particularly cod-liver oil, was more pronounced than that of sunflowerseed oil. The hypotensive effect of partially hydrogenated fish oil was less pronounced than that of cod-liver oil. Our experiments demonstrated a significant effect of the amount of dietary fat on the development of experimental hypertension. Greater intake of salt and animal fats in human diet may be one of the causes of essential hypertension.