Background: Blood pressure (BP) is a strong determinant of cardiovascular diseases (CVD). The strength of this association in 2 Japanese communities with different intakes of fish was investigated. Methods and Results: The analysis was carried out in the Japanese cohorts of the Seven Countries Study (Tanushimaru and Ushibuka), which were followed for 40 years. We included 1,006 subjects for whom data on baseline BP and relevant potential confounders were available. Data were analysed using multivariable Cox proportional hazard models. In Tanushimaru men, the systolic BP level was strongly directly related to risk of stroke and CVD mortality, with hazard ratios (HR) of 4.42 (2.02-9.70) for stroke and 3.05 (1.73-3.25) for CVD for BP levels ≥140mmHg compared to <120mmHg. In Ushibuka, the HR were 1.74 (0.91-3.32) for stroke mortality and 1.66 (1.01-2.75) for CVD mortality for high vs. low systolic BP. With regard to diastolic BP, the associations with stroke and CVD mortality were similar in Tanushimaru and Ushibuka subjects. Conclusions: This study showed that the well-known relationship of systolic BP with stroke and CVD mortality was more pronounced in the Japanese farming community than in the fishing community. This brings up the hypothesis that the detrimental effect of raised systolic BP could be attenuated by a high intake of fish. (Circ J 2011; 75: 1890-1896)