['To assess the association between weight status and dental caries among 12-year-old Brazilian schoolchildren.', 'This cross-sectional study was carried out in Porto Alegre using a multistage probability sampling strategy to draw a representative sample of schoolchildren attending public and private schools. Data on demographics, socioeconomic status, oral hygiene habits, anthropometrics, and dental caries were collected. Overweight and obesity were defined according to WHO categories for BMI (body mass index)-for-age Z-scores. Survey Poisson regression models were used to assess the association between weight status and dental caries. Estimates were adjusted for gender, socioeconomic status, and brushing frequency. Prevalence ratios (PR), rate ratios (RR) and 95% confidence intervals (95% CI) were reported.', 'One thousand five hundred and twenty-eight of 1837 eligible schoolchildren were examined. Prevalence of overweight and obesity were 22.15% (95% CI = 20.59-23.72) and 13.61% (95% CI = 11.44-15.78), respectively. Caries experience was observed in 55.23% (95% CI = 45.26-65.19) of children. Schoolchildren presented, on average, 1.39 (95% CI = 1.07-1.71) decayed, missing or filled teeth. No significant differences in caries experience or extent were observed among BMI groups. After adjusting for important cofactors, weight status was not associated with caries prevalence (overweight, PR = 0.99; 95% CI = 0.89-1.10; obese, PR = 1.00; 95% CI = 0.87-1.16) or caries extent (overweight, RR = 0.91; 95% CI = 0.74-1.12; obese, RR = 0.86; 95% CI = 0.72-1.04).'] Are overweight and obesity associated with dental caries among 12-year-old South Brazilian schoolchildren?