OBJECTIVE: To examine behavioural characteristics of subjects with successful long-term weight reduction. DESIGN: Prospective cohort study with 3?y follow-up. SETTING: Multicentre study of participants of a commercial weight-reduction programme (BCM-Programme). SUBJECTS: Until February 2000, 6857 voluntary study participants were included. Analyses are based on 1247 subjects with complete 3?y data. INTERVENTIONS: Open-group dietary and behavioural counselling with initial meal substitutions. RESULTS: Subjects show a number of significant behavioural improvements, for example, choice of low-fat food, flexible control of eating behaviour and coping with stress. Subjects who maintain these changes by the end of the first year have a higher probability of successful weight reduction after 3?y. CONCLUSIONS: Successful weight maintenance is associated with more pronounced improvements of health behaviours after 1?y. The likelihood of success increases with the number of behavioural patterns which are involved in the process of change.