The primary objective of this study will be to evaluate the effect of introducing two levels of environmental programs, in addition to existing individualized programs, at reducing obesity in the workplace. Five outcomes will be evaluated: 1) body mass index and other weight-related biometric measures; 2) behavioral health risk factors; 3) weight-related health conditions; 4) health care utilization and medical expenditures; and 5) employee productivity measured in terms of reduced absenteeism and on-the-job presenteeism. The study will also include an assessment of costs and benefits of the two programs, including the medical, absenteeism, and productivity benefits, and an assessment of the impact of the programs on the worksite climate. Twelve Dow chemical companies will participate in the study. Participants will be randomly assigned to a moderate environmental program, an intensive environmental program, or a control group, which will receive individualized treatment only. The moderate program will include inexpensive environmental changes (e.g., prompts and reminders). In the high intensity program, senior managers will assist in the development of a worksite culture that is broadly supportive of improved weight and health management by employees. Annual health screening and biometrics data along with administrative medical claims, absence records, and productivity survey data will be analyzed to determine program impacts. Non-experimental statistical methods will be used to control the differences that remain across sites after randomization. The study will also produce extensive information about how employers can successfully implement environmental programs to reduce obesity at worksites.