Regular exercise has been well established to be of physical and psychological benefit to the growing child. Recently, the issue of sudden death during sport has been brought to public attention after the tragic deaths of a few high profile athletes. The need for screening before participation has been queried and task forces have been established to devise recommendations in this area. Physicians are also being faced with a growing population of children and young adults with complex congenital heart defects who are surviving thanks to advances in medical and surgical treatment. An understanding of the residual haemodynamic lesions in these children is essential in order to make sensible recommendations for their ongoing participation in sport. The role of the physician is to impose sensible restrictions based on an assessment of the patient’s potential risk of sudden death and of deterioration of cardiac haemodynamics as a result of sport while at the same time encouraging participation in sport as much as is safely possible.