So-called 'absent pulmonary valve syndrome' is a rare cardiac malformation, usually associated with tetralogy of Fallot. Congenital absence of the leaflets of the pulmonary valve is less common when the ventricular septum is intact. Characteristic features of the syndrome include dysplasia or absence of the pulmonary valvar leaflets, permitting severe pulmonary regurgitation, and aneurysmal dilation of the pulmonary arteries. The purpose of our study was to review our experience with patients diagnosed as having the absent pulmonary valve syndrome, and to describe their clinical presentation, natural history, and outcome. We reviewed retrospectively data from 18 patients with absent pulmonary valve syndrome, 10 boys and eight girls, treated between March 1983 and May 2003. We identified two groups of patients, one made up of 11 patients with a ventricular septal defect, in whom the morphology of the subpulmonary outflow tract was phenotypic for tetralogy of Fallot, and another group, with seven patients, having an intact ventricular septum. Family history of congenital heart disease was common only in patients with ventricular septal defect, being found in 73%, all of whom were diagnosed during infancy with variable respiratory distress. Diagnosis was delayed in 43% of the patients with an intact ventricular septum. Cardiac surgery was performed in eight patients with ventricular septal defect (73%), compared to only two patients (28%) with an intact ventricular septum. Overall mortality was 28%, with five patients dying. Although our sample was small, two clinical patterns emerged depending on the presence or absence of a ventricular septal defect. Patients with a ventricular septal defect and phenotypic features of tetralogy of Fallot have a strong family history of congenital cardiac disease, develop respiratory symptoms during infancy and exhibit a variable prognosis, despite cardiac surgery. Patients with an intact ventricular septum are usually asymptomatic, present later in life, and show a relatively benign prognosis.