Objective: To examine first-year results from a workplace environmental obesity prevention program at The Dow Chemical Company. Methods: A quasi-expenmental cohort study was conducted among employees at nine treatment worksites (n = 8013) who received environmental weight management interventions and three control worksites (n = 2269). Changes in employees' weight, body mass index (BMI), and other health risks were examined using X² and t-tests. Results: After 1 year, a modest treatment effect was observed for weight and BMI largely because the control group subjects gained weight; however, no effect was observed for overweight and obesity prevalence. Other nsk factors (tobacco use, high blood pressure, and systolic and diastolic blood pressure values) decreased significantly, although blood glucose (high nsk prevalence and values) increased. Conclusions: Environmental changes to the workplace can achieve modest improvements in employees' health nsL·, including weight and BMI measures, in 1 year.