In the present work we investigated the usefulness of olive oil in a standard hypolipidemic diet suitable for the secondary prevention of atherosclerosis. Some patients who had received a diet with a P/S value of 1.3 were turned to a diet, rich in olive oil, with a P/S ratio of 0.52; the same number of patients were fed on with the initial diet. The main differences we found were a decrease of LDL cholesterol parallel to an increase of HDL cholesterol in the patients fed on the diet rich in olive oil. No modifications were found in these patients as far as hemostatic function and liver functional tests are concerned.