In cardiopulmonary exercise testing with children and adolescents, age specific protocols are used together with tools adjustable to their body dimension and development. Assessing weight, height und pubertal stage is a prerequisite for the interpretation of every test. Indications for exercise testing are airway symptoms and findings limited performance, chronic diseases, planning of trainings and scientific studies. The more tests are standardized and used on a large scale, the more normal values are available to compare individual results. However, the interindividual variability of measured values is high, depending as much from the developmental stage of the individual as from protocols, tools and the performing laboratory.