Motor fitness and physical activity are important aspects of a healthy development in childhood and adolescence. However, the assessment of motor fitness and physical activity is not subject to standardized criteria; furthermore, the samples investigated do not provide a representative image of the whole population. Therefore, the existing data only allow very limited statements on the state and development of motor fitness and physical activity. The "Motorik" module, as part of the German Health Interview and Examination Survey for Children and Adolescents (KiGGS), offers nationwide representative data on the motor fitness and physical activity of children and adolescents for the first time. Besides the baseline-analysis, another aim is to analyse the complex relationship between motor fitness, physical activity and health. Motor fitness, based on the systematisation of motor abilities, was assessed using a test profile. The test profile consists of 11 items measuring cardiorespiratory fitness, strength, coordination and mobility. Physical activity was assessed using a questionnaire containing 51 items on the duration, intensity and frequency of physical activity in everyday life, during leisure time, at school and in sports clubs. The above-mentioned questionnaire subtopics were supplemented by questions on the weekly prevalence of at least 60 minutes of daily physical activity, on material and local conditions, as well as on cognition and motivation for physical activity. In the years 2004 to 2006, the motor fitness and physical activity of 4,529 children and young people between the ages of 4 and 17 years was investigated on 168 sample points in the context of the "Motorik" module. Half of the children and adolescents investigated belong to the middle class, approximately 15% have a background of migration. The majority of the subjects come from small towns, about a quarter live in the city, less than 20% are settled in rural areas.