Awaiting heart or heart-lung transplantation is a time of extreme stress for child and family, but there has been little evaluation of the psychosocial morbidity in this population. This preliminary study monitored changes in the mental health status of these children and their families. Fifty-one children considered suitable for transplantation and their families were assessed at the time of acceptance onto the waiting list and 6 months later. Twenty-five percent of the children had a psychiatric disorder, and 60% had a degree of impairment in psychosocial functioning. These high levels of morbidity indicate the need for a more comprehensive approach to treatment for this population.