The aim of the present study was to evaluate the validity of the estimated prevalence of childhood obesity from height and weight reported by parents. The subjects were 170 first-grade children (83 males and 87 females) and 206 fourth-grade children (99 males and 107 females). A questionnaire including questions on height and weight was distributed to children and completed by parents. Anthropometric measurements were conducted in the standard way. Ageand sex-specific cut-off points linked to adult overweight were employed to determine childhood obesity. The correlation and difference between reported and measured values were calculated separately for grade and gender. Correlation coefficients ranged from 0.90 to 0.96 for height, 0.95 to 0.99 for weight, and 0.86 to 0.97 for body mass index (BMI). Sensitivity and specificity, the indices predicting the presence or absence of actual obesity from reported height and weight, ranged from 83.3 to 93.3 % and 96.3 to 98.9 %, respectively. The estimated prevalence of obesity (as calculated by reported data) minus actual prevalence (as calculated by measured data) ranged from -1.2 to 1.0 %. These results indicate that height and weight reported by parents provides a reliable assessment of childhood obesity. J Epidemiol, 2002 ; 12: 9-13