Childhood overweight and obesity is a public health concern not just because of its growing prevalence but also for its serious and lasting health consequences. Though height and weight measures are easy to obtain and New Hampshire Head Start sites measure height and weight of their enrollees, there are numerous challenges related to accurate measurement and assessment at the individual and population level. Problems may arise from a lack of standardized equipment, measurement inaccuracies, use of inappropriate reference data, cutoff points, and incorrect estimation of BMI percentiles. Considering these challenges, the authors designed and implemented a project in which Head Start personnel, public health professionals, and researchers closely collaborated. They performed the first standardized survey of body mass index (BMI) among children from low-income families attending the New Hampshire Head Start Program. The goal of this project was to obtain accurate, directly measured data representative of height and weight status of 3- to 5-year-old enrolled children. The intended use for the data was to assess the baseline of overweight and obesity and further to plan and evaluate prevention and intervention efforts targeting this specific population of children. This article summarizes the findings and implication of a surveillance survey that assessed the prevalence of overweight and obesity among New Hampshire Head Start children.