Infants who survive open-heart surgery are at risk for developmental disability, which may impact on the well-being not only of the child, but also the family. The objective of our prospective study, therefore, was to determine the long-term health-related quality of life of children with congenital cardiac malformations following open-heart surgery, and to describe the persisting level of stress in their families. To this end, 49 parents completed the Child Health Questionnaire, the Parenting Stress Index, and the Child Behaviour Checklist as part of a developmental follow-up protocol when their child was 5 years of age. Mean scores on the Child Health Questionnaire were in the normal range, with physical well-being equal to 53.5, psychosocial well-being 50.9, with only 6.4 percent and 8.5 percent of subjects, respectively, falling within the suboptimal range of less than 40. The distribution of scores on the Parenting Stress Index, however, were more variable, with over one-quarter of parents indicating a high level of stress, with almost one-fifth having low levels of stress, and just over half scoring in the normal range, with the group mean being 52.6 plus or minus 32.3. An abnormal neurologic examination before surgery was associated with lower physical health (beta equal to -5.5, p equal to 0.02, r2 equal to 0.18), whereas lower arterial saturations of oxygen, less than 85 percent preoperatively, was associated with lower psychosocial health (beta equal to -6.6, p equal to 0.01, and r(2) equal to 0.14). The internalizing and externalizing behaviours of the child were significantly correlated with psychosocial well being, with r ranging from -0.32 to -0.52, and p less than 0.05. Parental stress also correlated with psychosocial health (r equal to -0.48 and p equal to 0.0009). Overall, the perception by the parents of the health-related quality of life of their child is favourable 5 years following open-heart surgery during infancy. Many parents, nonetheless, continue to feel either stressed or defensive about their child, particularly if their child exhibits behavioural difficulties. Our findings suggest that strategies need to be considered to enhance family well-being in the planning and delivery of health services to this population at high risk.