In children with congenital heart disease, interest concerning cardiovascular performance capacity is directed mainly to the operated patient. Indirect and/or submaximal tests to assess cardiovascular ability are based on assumptions that are at least partially incorrect, so that test results may not be valid. Standardization of values should be performed according to body height, but should also account for age. There is a lack of information concerning the cardiovascular performance capacity of children following Senning or Mustard operations for transposition of the great arteries and following Fontan procedures for different malformations. In considering participation in sports, it should be realized that it is not the cardiovascular performance capacity that generally plays a dominant role. In technical disciplines and in short-term efforts, motor performance may be more important. Endurance training cannot be recommended in view of the anatomical disorders still present in many patients after cardiac surgery. Ergometry can add information on dysrhythmias, which may cause problems postoperatively, but may also be present without organic heart disease.