There are several studies indicating an association between C-reactive protein (CRP) and blood pressure (BP) in the Japanese population, but the influence of physical activity has not been considered. Therefore, we designed a cross-sectional survey to determine whether leisure-time physical activity (LTPA) modifies the relation between CRP and hypertension among Japanese elderly. Our study population comprised 643 subjects aged 70 years and over in whom CRP, home BP, and self-reported LTPA were measured. LPTA was categorized into three levels of intensity--walking, brisk walking, and sports-and a questionnaire was used to estimate the level in each patient. Hypertension was defined as a home systolic BP of 135 mmHg or over and/or home diastolic BP of 85 mmHg or over or current use of antihypertensive agents. LTPA levels were associated with both CRP and hypertension. After adjustment for factors affecting CRP and hypertension, and additional adjustment for LTPA levels, the odds ratio (95% confidence interval) of hypertension by CRP was 2.21 (range: 1.33-3.72), 1.99 (1.17-3.42), and 2.38 (1.36-4.21) times higher in subjects in the second, third, and fourth quartiles of CRP, as compared to subjects in the first quartile, respectively. A multiple regression model showed a positive and significant relation between log-transformed CRP and systolic BP after adjustment for potential confounding factors when participants taking antihypertensive medication were excluded. This is the first study to clarify that the positive significant relation between CRP and hypertension was independent of LTPA levels among Japanese elderly.