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Participant retention is a major challenge in long-term randomized controlled trials of behavioral lifestyle interventions.1 There is evidence that attrition in randomized behavioral weight-loss studies is associated with treatment-related factors including random assignment to the ‘control’ group 2 and dissatisfying weight loss outcomes early in the intervention.3 Moreover, there may be behavioral and psychosocial factors at baseline that are overlooked during screening or enrollment, but predict poor retention. Previous studies indicate that number of weight loss attempts, poorer quality of life, mental illness, lack of exercise, and lack of self-efficacy to increase physical activity at pretreatment are associated with attrition.4,5 Look AHEAD (Action for Health in Diabetes) is a 16-center randomized clinical trial of an intensive weight loss intervention for overweight and obese adults with type 2 diabetes.6 The main purpose of Look AHEAD is to examine the long-term effects of weight loss on incidence of major cardiovascular events.6 Participants were enrolled from 2001 to 2004, and one-year7 and four-year 8 results have been published. Participant follow-up rates have been 93% or greater each year between year one and year four.7,8 Thus, Look AHEAD presents a unique opportunity to examine predictors of missed follow-up visits in a large-scale, long-term randomized clinical trial of a lifestyle intervention. We analyzed data from the first 48 months of Look AHEAD to identify behavioral and psychosocial factors at baseline that predict missing two consecutive 6-month data collection visits (defined in the study as ‘inactive status’).