In order to investigate the prevalence and risk factors for hypertension, and the association between reported physical activity and newly-diagnosed hypertension in Taiwan, 1,103 subjects randomly sampled from 6,725 residents, aged over 20 years from Nanhwa Township, Tainan County, Taiwan, were examined. Questionnaire interviews as well as blood pressure and anthropometric measurements were completed for 479 participants (adjusted response rate, 71.1%) in 1994. The prevalence of hypertension age-sex-standardized to the population of Taiwan in 1992 was 17.8% for adults aged over 20 years and 33.3% for those aged over 40 according to the Fifth Report of the Joint National Committee on Detection, Evaluation and Treatment of High Blood Pressure (systolic > or = 140 and/or diastolic > or = 90 mmHg), and 11.3% and 22.0%, according to the World Health Organization (systolic > or = 160 and/or diastolic > or = 95 mmHg). Education level, socioeconomic status, history of heart disease and diabetes, family history of hypertension, body mass index, waist-to-hip ratio and physical activity level were all correlated with newly-diagnosed hypertension prevalence after adjustment for age and sex. In a multiple logistic regression model, physical activity, especially low sports activity, was an independent risk factor for hypertension after adjustment for age, sex, body mass index, waist-to-hip ratio and family history of hypertension.