The objective was to assess weight-loss maintenance in individuals who successfully completed a commercial weight-loss programme at multiple sites in the United States. A total of 699 lifetime members of Weight Watchers represented the national sample and 217 additional lifetime members served as an oversample. Lifetime members were asked to self-report their current weight 1, 2, and 5 years after they had successfully completed the programme. Additional lifetime members served as an oversample whose weights were measured. The discrepancy between reported and measured weight in the oversample was used to adjust the self-reported weights of the national sample. Seventy-one percent of participants were middle-aged or older and 95.3 % were female; their mean starting BMI was 27.6 (sd 3.6) kg/m2. The percentage of Weight Watchers lifetime members who maintained at least 5 % of their weight loss 1, 2 and 5 years after successful completion of the programme was 79.8, 71.0, and 50.0, respectively. The percentage of participants who remained below their goal weight 1, 2 and 5 years after completion of the programme was 26.5, 20.5, and 16.2, respectively. Results obtained with this group of successful Weight Watchers members are not directly comparable to those obtained with clinical samples of obese dieters because the current sample comprises only the most successful Weight Watchers participants. However, these results provide further evidence that maintenance of weight loss in those who successfully lose weight in one commercial weight-loss programme is more feasible than data from clinical populations have suggested.