BACKGROUND: Some cross-sectional studies suggest that fiber and protein intake can be associated with lower levels of blood pressure, but results from prospective cohorts are scarce and none has been conducted outside the U.S. METHODS: The SUN cohort followed-up prospectively 5880 Spanish men and women older than 20 years of age, all university graduates. Dietary information was gathered at baseline with a previously validated semiquantitative food frequency questionnaire. New cases of medically diagnosed hypertension (HT) were identified through responses to a mailed questionnaire after at least 2 years from recruitment. RESULTS: One hundred and eighty new cases of HT were ascertained after a median follow-up of 28 months. After adjustment for potential confounders and several dietary factors, participants in the highest quintile of vegetable protein intake had a lower risk of incident HT compared with those in the lowest quintile [hazard ratio (HR) = 0.5, 95% confidence interval (CI) 0.2-0.9, p for trend = 0.06]. Similarly, fiber from cereals was inversely associated with a lower risk of HT (HR comparing fifth vs. first quintile = 0.6, 95% CI 0.3-1.0, p for trend = 0.05). Risk reduction was more important among men and obese and older individuals. Total or animal protein and total fiber as well as fiber from other sources different from cereal were not associated with the risk of HT. CONCLUSIONS: In this Mediterranean cohort, dietary intake of vegetable protein and fiber from cereals was associated with a lower risk of HT when other nutrients were also taken into consideration.