Objective. Mutations in the fibrillin-1 gene are the cause of Marfan syndrome. We wanted to investigate the relationship between a mutation in this gene and risk of prevalent hypertension. Methods. In a cross-sectional study, the effect of a G-A substitution in intron 27 in the fibrillin-1 gene (rs11856553) on risk of prevalent hypertension was studied in two large population-based studies: the Health 2006 study, consisting of 3193 women and men, age 18-69 years, and the MONICA10 study, consisting of 2408 women and men, age 41-72 years. In 1646 MONICA10 participants, blood pressure (BP) was also measured by 24-h ambulatory recordings. Results. Among the 3193 Health 2006 participants 23 had the G-A variant, and among the 2408 MONICA10 participants 18 had the G-A variant. In Health 2006, the odds ratio estimate (95% confidence intervals) for the G-A variant for risk of hypertension, defined as systolic (S) BP =¿140 mmHg or diastolic (D) BP =¿90 mmHg or on antihypertensive medicine, was 2.67 (1.14-6.18), p =¿0.022. The corresponding figure for moderate to severe hypertension, defined as SBP =¿160 mmHg or DBP =¿100 mmHg, was 9.68 (4.24-22.12), p