In India, rotavirus infections cause the death of 98621 children each year. In urban neighbourhoods in Delhi, children were followed up for 1 year to estimate the incidence of rotavirus gastroenteritis and common genotypes. Infants aged ⩽1 week were enrolled in cohort 1 and infants aged 12 months (up to +14 days) in cohort 2. Fourteen percent (30/210) gastroenteritis episodes were positive for rotavirus. Incidence rates of rotavirus gastroenteritis episodes in the first and second year were 0·18 [95% confidence interval (CI) 0·10–0·27] and 0·14 (95% CI 0·07–0·21) episodes/child-year, respectively. The incidence rate of severe rotavirus gastroenteritis in the first year of life was 0·05 (95% CI 0·01–0·10) episodes/child-year. There were no cases in the second year. The common genotypes detected were G1P (27%) and G9P (23%). That severe rotavirus gastroenteritis is common in the first year of life is relevant for planning efficacy trials.