Overweight and obese children are more likely to develop risk factors that can lead to respiratory, metabolic, and cardiovascular illness. The increase in prevalence of childhood overweight and obesity in the United States since the 1960s has been well documented. In New York City, in 1996, an estimated 19.7% of third grade children and 21.2% of sixth grade children in public and private schools were found to be overweight; in 2003, an estimated 43% of the city's public elementary school students were found to be overweight, and 24% of these students were obese. To update city data on childhood obesity and evaluate public health interventions, the New York City Department of Health and Mental Hygiene analyzed body mass index (BMI) data for public schoolchildren in kindergarten through eighth grade (K-8), using data from the 2006-07 to 2010-11 school years. This report summarizes the results of that analysis, which found that, overall, the prevalence of obesity in grades K-8 decreased 5.5%, from 21.9% in 2006-07 to 20.7% in 2010-11. Obesity decreased significantly among children in all age groups and in all socioeconomic and racial/ethnic populations; however, the decrease was smaller among black (1.9%) and Hispanic (3.4%) children than among Asian/Pacific Islander (7.6%) and white (12.5%) children. Despite the decreases in obesity, continued public health interventions are needed to further reduce the prevalence of obesity and to eliminate disparities among schoolchildren in New York City.