OBJECTIVE To assess the clinical, functional state, and complications late (15-20 years) after palliative Mustard operation. METHODS Examination and evaluation of all patients presenting in adolescence and adult life after palliative Mustard operation for transposition of the great arteries and pulmonary vascular disease. METHODS Grown-up Congenital Heart Unit specialised in the care of adolescents and adults with congenital heart disease, designated as having "quaternary" status within a tertiary referral centre for cardiac diseases. METHODS Database searched for patients referred after palliative Mustard for classic transposition of the great arteries. Ten patients aged 18-31 (mean (SD) 25.9 (5.2)) years with a palliative Mustard operation performed at age 1.7-15 (mean (SD) 9 (4.6)) years were fully evaluated by echocardiography, exercise testing, Holter monitoring, and magnetic resonance imaging or radionuclide ventriculography, or both 15-20 years later. RESULTS One patient died aged 25 years with biventricular failure (ability index 3/4), haemoptysis, and atrial flutter, eight were well (ability index 2), and one disabled (ability index 3). Arterial oxygen saturation at rest was 85-98% (mean (SD) 93.8 (4)%) decreasing to 59-87% (mean 77 (9.5)%) after limited exercise. Symptomatic arrhythmias occurred in four patients, atrial flutter being the most common, and two had sinus node dysfunction. Significant tricuspid regurgitation occurred in four patients. CONCLUSIONS Patients with palliative Mustard operation have a low incidence of symptomatic ventricular dysfunction and despite exercise limitation by hypoxia, continue to live active, near normal lives until their thirties.