OBJECTIVE To identify risk factors for loss to cardiology follow-up among children and young adults with congenital heart disease. METHODS We used a matched case-control design. Cases were born before January, 2001 with moderate or complex congenital heart disease and were previously followed up in the paediatric or adult cardiology clinic, but not seen for 3 years or longer. Controls had been seen within 3 years. Controls were matched 3:1 to cases by year of birth and congenital heart disease lesion. Medical records were reviewed for potential risk factors for loss to follow-up. A subset of cases and controls participated in recorded telephone interviews. RESULTS A total of 74 cases (66% male) were compared with 222 controls (61% male). A history of missed cardiology appointments was predictive of loss to follow-up for 3 years or longer (odds ratio 13.0, 95% confidence interval 3.3-51.7). Variables protective from loss to follow-up were higher family income (odds ratio 0.87 per $10,000 increase, 0.77-0.98), cardiac catheterisation within 5 years (odds ratio 0.2, 95% confidence interval 0.1-0.6), and chart documentation of the need for cardiology follow-up (odds ratio 0.4, 95% confidence interval 0.2-0.8). Cases lacked awareness of the importance of follow-up and identified primary care physicians as their primary source of information about the heart, rather than cardiologists. Unlike cases, controls had methods to remember appointments. CONCLUSIONS A history of one or more missed cardiology appointments predicted loss to follow-up for 3 or more years, as did lack of awareness of the need for follow-up. Higher family income, recent catheterisations, and medical record documentation of the need for follow-up were protective.