The excellent quality of the Mediterranean Diet, apart from other products, is associated to a high consumption of fish. Epidemiological studies have shown over time certain beneficial effects of fish consumption in the prevention of chronic diseases. The specific components found in fish, the long chain omega 3 eicosapentanoic and docosahexanoic fatty acids, have been identified as the principle elements responsible for this protective effect in Mediterranean populations. There is also evidence for a relationship between elevated fish consumption and reduced cardiovascular mortality, especially in populations at greater risk for this disease or those with high fatty fish intakes. Moreover, fish consumption of > or = 3.5 servings/week appears to have a protective effect against certain site specific cancers, and is also associated with a number of lifestyle factors. It's been shown that this protective effect is reduced in those who smoke, consume alcohol, are less physically active and who consume fish preserved in salt. However, these preventive effects are seen fundamentally when lipid profiles approximate those typical of the Mediterranean Diet, which is also rich in monounsaturated fatty acids. In light of new evidence, current nutritional objectives for the Spanish population recommend that polyunsaturated fatty acids account for 5% of total calories, with an omega6:omega3 ratio ranging from 6/1 to 10/1.