We report on a standardized survey of height and weight status of children attending the New Hampshire Head Start Program during the 2007-2008 school year. Baseline prevalence estimates of overweight and obesity are needed for obesity prevention activities and intervention. We selected a random one-stage cluster sample and screened 629 children ages 3-5 years attending 27 of 45 Head Start sites. Survey participants underwent standardized height and weight measurements. We recorded sex and date of birth and calculated body mass index (BMI). For each participating site, we determined rural or urban status. We assessed prevalence of overweight and obesity for the survey sample and the statistical significance of differences between subgroups. Prevalence of overweight (BMI greater than or equal to 85th and less than 95th percentile) was 18.4% (95% confidence interval [CI]: 16.5%-20.4%), and prevalence of obesity (BMI greater than or equal to 95th percentile) was 18.1% (95% CI: 16.1%-20.2%). No statistically significant differences were noted by age or sex. Children attending urban sites were found to be significantly more likely obese when compared with children attending rural sites. Children enrolled in New Hampshire Head Start demonstrate an increased prevalence of overweight and obesity compared with the general population. There are marked differences in the prevalence of obesity by urban/rural sites. Specific interventions for Head Start children are warranted. (Contains 1 table.)