The aim of the study is to determine the prevalence of hypertension (HTN) and its risk factors in urban and rural India. In Phase I of the Indian Council of Medical Research-India Diabetes (ICMR-INDIAB) study, individuals aged ⩾20 years were surveyed using a stratified multistage sampling design, in three states (Tamil Nadu, Maharashtra and Jharkhand) and one union territory (Chandigarh) of India. Blood pressure was measured in all study subjects (n=14 059). HTN was defined as systolic blood pressure ⩾140 mm Hg, and/or DBP ⩾90 mm Hg and/or use of antihypertensive drugs. Overall age-standardized prevalence of HTN was 26.3% (self-reported: 5.5%; newly detected: 20.8%). Urban residents of Tamil Nadu, Jharkhand, Chandigarh and Maharashtra (31.5, 28.9, 30.7 and 28.1%) had significantly higher prevalence of HTN compared with rural residents (26.2, 21.7, 19.8 and 24.0%, respectively). Multivariate regression analysis showed that age, male gender, urban residence, generalized obesity, diabetes, physical inactivity and alcohol consumption were significantly associated with HTN. Salt intake ⩾6.5 g per day, showed significantly higher risk for HTN (odds ratio: 1.4, 95% confidence interval: 1.0-1.9, P=0.042) even after adjusting for confounding variables. In conclusion, prevalence of undiagnosed HTN is high in India and this calls for regular screening.