In 2004, the National Heart, Lung, and Blood Institute funded seven independent research projects to test the effectiveness of multicomponent weight control interventions at worksites that include environmental changes alone or in combination with individually targeted strategies (Pratt et al, Obesity. 2007;15:2171-2180). The studies were conducted in a variety of worksites across the United States. This supplement to the Journal of Occupation and Environmental Medicine includes a series of manuscripts that evaluate various aspects of the funded studies, including environmental and cost-related findings, process evaluation, and the impact of acute and chronic psychosocial work stressors on body mass index.