A positive association between nephrolithiasis and blood pressure has been suggested in previous studies. However, controversy remains, due to methodological problems in some of the previous studies and absence of prospective data. We evaluated the relationship between nephrolithiasis and the risk of hypertension in a cohort of 51,529 men followed prospectively for 8 years. Information was obtained by biennial mailed questionnaires. At baseline in 1986, 4111 (8.0%) subjects reported a history of nephrolithiasis and 11,623 (22.6%) a diagnosis of hypertension. A positive association was found between the two disorders (age adjusted odds ratio [OR]: 1.31; 95% confidence interval [CI]: 1.30 to 1.32). Among men who reported both disorders, 79.5% reported that the occurrence of nephrolithiasis was prior to or concomitant with the diagnosis of hypertension. Among men without hypertension at baseline, the odds ratio for incident hypertension in men with a history of nephrolithiasis compared with those without was 1.29 (95% CI: 1.12 to 1.41; adjusted for age, body mass index, and intake of calcium, sodium, potassium, magnesium, and alcohol). The occurrence of incident nephrolithiasis during follow-up was similar in men with hypertension at baseline compared with that in men without (adjusted OR: 0.99, 95% CI: 0.82 to 1.21). These data support the hypothesis that prior occurrence of nephrolithiasis increases the risk of subsequent hypertension.