The aim of the study was to compare group and individual weight reduction programmes in the treatment of severe obesity. The study population included 40 women and 20 men, mean age 41 years. The mean body mass index was 43.5 kg/m2 in women and 42.2 kg/m2 in men. The subjects were randomly divided into two groups, one with group counselling (GC group) and the other with individual counselling (IC group). The treatment programme of the GC group consisted of a two-week weight reduction period in a rehabilitation centre followed by group sessions for two years. The programme of the IC group consisted of individual counselling and follow-up by a physician. The adherence rate of the follow-up examinations was 97% at two years and 88% at five years. In the GC group the mean weight reduction in women at three months and at one, two and five years was 15.6, 15.7, 5.4 and 2.1 kg and in men 14.9, 13.1, 1.8 and 3.0 kg, respectively. In the IC group the corresponding values for women were 8.4, 11.9, 10.4 and 3.4 kg and for men 17.0, 26.2, 15.6 and 12.9 kg. Self-reported and measured weights at the five-year follow-up were closely correlated (r = 0.99). Weight loss during the first three months predicted a good result at two and five years. The results showed that group counselling starting with an in-patient period led to rapid weight reduction, but a better and more sustained effect was achieved by individual counselling, especially in men.