Based on the national part of the international "The Health Behaviour in School-aged children" (HBSČ) study, the authors present the incidence of overweight and obesity in 11-year, 13-year and 15-year old children in the czech Republic. Furthermore they focus on the relationship between excess weight and certain socio-demographic factors, eating habits and diet strategies. The results were obtained from 4,724 children from 87 randomly selected schools. 16 per cent of the children were found to be overweight; 2.6 per cent of the children were obese. A higher prevalence of overweight was found in boys (18 per cent) than in girls (14 per cent). The highest number of overweight children was in the 11-year old age group. The number of overweight children significantly decreased between the llth and 15th year of age, especially in girls. The children's reaction towards obesity changed significantly with gender and age. The decrease in the number of overweight girls was probably connected with the tendency toward dieting which markedly increases with age. Although even 11-year old boys perceive being overweight a problém to which they respond in accor-dance with standard dietary recommendations, with growing age they were less willing to statě that they limit their food intake because of being overweight, or that they should limit it. Overweight boys exercised more often, overweight girls limited their food intake more often. However, even girls with normál body weight followed weight reduction diets and even boys with normal body weight stated that they exercised because of their figure. In the higher age group, children were eating more frequently outside their famili-es, both for dietary and other reasons, and they were skipping one of the main meals of the day (usually breakfast). This was especially marked in overweight children and could háve been a contributing factor to their excess weight. From the sociodemographic factors that were followed, it was confirmed that parents with higher education are less likely to have obese children and that there are more obese children in the čzech countryside than in towns. No correlation was found between child obesity and factors such as a nuclear family, the number of siblings, grandparents in the family

        Key words: obesity, overweight, diets, eating habits, adolescence