The aim of this study was to test the hypothesis of association between low birthweight and dental caries. This study used data from the Third National Health and Nutritional Examination Survey, 1988-94 (NHANES III) including 7- to 11-year-old children with complete dental caries information (n = 2439). Two case definitions for dental caries were used: presence of the disease in more than one tooth, and more than 10% of teeth with dental caries. Low birthweight was defined as those children born weighing <2500 g. Other covariates used in the analysis were sex, age, poverty level, race/ethnicity, frequency of dental visit, education of head of household, daily sucrose intake, blood lead level and blood cotinine level. A separate analysis was conducted for each case definition of dental caries. Bivariable and stratified analysis was performed followed by multivariable Poisson regression. The Stata 8.0 statistical package was used to take into consideration the multistage complex sample. For the definition of more than one tooth with dental caries, the prevalence ratios (PRs) for bivariable and multivariable analyses were 1.28 [95% confidence interval (CI): 0.48, 3.42] and 1.01 [95% CI: 0.41, 2.49] respectively. For the definition of >10% of teeth with dental caries, the PRs for bivariable and multivariable analyses were 1.33 [95% CI: 0.60, 2.96] and 1.32 [95% CI: 0.75, 2.30] respectively. This study could not demonstrate an association between low birthweight and dental caries in permanent teeth of 7- to 11-year-old American children.