OBJECTIVE: Cohort study (the SUN project) to identify dietary determinants of hypertension, diabetes, obesity and coronary heart disease (CHD), among other conditions. DESIGN: The SUN project is a Mediterranean dynamic prospective follow-up (cohort) study assessing participants every 2 years. The recruitment started in 2000 and it is permanently open (this is a dynamic cohort). A preliminary case-control study of myocardial infarction was also conducted, selecting incident cases of myocardial infarction and matched hospital controls. SETTING: The SUN study is conducted in Spain with university graduates, most of them being former students of the University of Navarra. The case-control study was conducted in three tertiary hospitals in the city of Pamplona (Spain). SUBJECTS: The case-control study included 171 cases and 171 controls. We have currently enrolled more than 17,500 participants in the SUN cohort. Approximately 7500 of them were enrolled less than 2 years ago, and have not received yet the invitation to complete the 2-year follow-up assessment. The follow-up rate for the first 10,000 participants approaches 90%. RESULTS: The case-control study found inverse associations between olive oil (or adherence to a Mediterranean food pattern) and myocardial infarction. In the SUN cohort, after 28.5 months of follow-up a higher adherence to a Mediterranean food pattern rich in olive oil was associated with a reduced risk of hypertension, though the results were statistically significant only among men. CONCLUSIONS: The SUN study and the accompanying case-control study support the benefits of a Mediterranean diet and olive oil against CHD and hypertension.