['To evaluate the current and ideal body weight perceptions of schoolchildren in relation to their actual body weight and socio-economic status (SES).', 'Baseline evaluation of schoolchildren from January 2008 to April 2008 as part of a 3-year longitudinal study.', 'City and non-city locations, Karnataka State, South India.', 'Schoolchildren (n 1877) aged between 8 and 14 years.', 'Girls, children of more educated parents and city dwellers were more likely to be overweight (P < 0.001). Younger children aged <10 years and those of lower SES were more likely to perceive themselves as underweight (adjusted OR = 1.63, 95 % CI 1.25, 2.11 and adjusted OR = 1.87, 95 % CI 1.32, 2.65). Underweight children were ten times more likely to overestimate their current weight status, while overweight children were four times more likely to underestimate it. The odds of children of lower SES underestimating their weight, as well as desiring a higher weight, were higher than those of higher-SES children.'] Is body weight perception associated with socio-economic status and current body weight in selected urban and rural South Indian school-going children?