BACKGROUND High attrition is a common problem for weight loss programs and directly affects program effectiveness. Since 2006, the Veterans Health Administration (VHA) has offered obesity treatment to its beneficiaries through the MOVE! Weight Management Program for Veterans (MOVE!). An early evaluation of this program showed that attrition rate was high. The present study examines how individual, facility, and program factors relate to retention for participants in the on-site MOVE! group program. METHODS Data for all visits to MOVE! group treatment sessions were extracted from the VHA outpatient database. Participants were classified into three groups by their frequency of visits to the group program during a six month period after enrollment: early dropouts (1 - 3 visits), late dropouts (4 - 5 visits), and completers (6 or more visits). A generalized ordered logit model was used to examine individual, facility, and program factors associated with retention. RESULTS More than 60% of participants were early dropouts and 11% were late dropouts. Factors associated with retention were older age, presence of one or more comorbidities, higher body mass index at baseline, lack of co-payment requirement, geographic proximity to VA facility, addition of individual consultation to group treatment, greater program staffing, and regular, on-site physical activity programming. A non-completion rate of 74% for on-site group obesity treatment poses a major challenge to reducing the population prevalence of obesity within the VHA. CONCLUSIONS Greater attention to individualized consultation, accessibility to the program, and facility factors including staffing and physical activity resources may improve retention.