The Prader-Willi syndrome is characterized by four cardinal symptoms i.e. hypotonia, hypogonadism, mental retardation and extreme obesity. Behavioural and psychological problems are frequent in these patients, mostly related to the withholding of food and the necessity of diet control. A treatment program has been developed for their eating problems. The treatment program is based on three points: 1. The importance of teaching them healthy eating habits within a specific eating culture. 2. The convinction that their obsession and fixation on food can be canalized and satisfied by being occupied, by playing and by learning about food. 3. The opinion that involvement and active participation in their diet is necessary to prevent behavioural problems and to stimulate "self control". The key objective of this program are to control the weight gain and to prevent behavioural problems. Based on these two main objectives, we developed a program based on four principles: a personal low calorie diet, the principles of behaviour modification, stimulation of motor skills and other developmental areas, and parental participation and education. This program is applied in group situation and in individual cases. The results of the present study in 4 children are encouraging. We noted an average weight loss of 2.25 kg, with an average increase of height of 3.5 cm. On intelligence testing we found that the scores on the performal subtests improved while the scores on the verbal subtests decreased. Little change occurred in the behavioural profile.