Exercise tests have been used for a long time as diagnostic tools for cardiac diseases. During recent years they have become more widely recognised as valuable instruments in the diagnosis and monitoring of pulmonary disorders. In the present issue of the European Respiratory Monograph, cardiopulmonary exercise testing for cardiac and pulmonary diseases has been presented. Techniques and equipment as well as reference values have been thoroughly described. The specific questions that arise in children have been addressed and exercise testing as a tool for the assessment of prognosis and treatment effects has been exhaustively presented.