The aim of this study was to determine the relative frequency of underlying illnesses for recurrent pneumonia in children. Children who had two or more episodes of pneumonia per year, or three or more episodes in a lifetime were investigated retrospectively at Ankara University Medical School, Department of Pediatric Infectious Diseases, between January 1997 and October 2002. Out of 788 children hospitalized for pneumonia, 71 (9 per cent) met the criteria for recurrent pneumonia. An underlying illness was demonstrated in 60 patients (85 per cent). In this group, the underlying illness was diagnosed prior to pneumonia in 11 patients (18.3 per cent), during the first episode in 12 patients (20 per cent), and during recurrence in 37 patients (61.7 per cent). Underlying diseases were bronchial asthma (32 per cent), gastroesophageal reflux (15 per cent), immune disorders (10 per cent), congenital heart defects (9 per cent), anomalies of the chest and lung (6 per cent), bronchopulmonary dysplasia (4 per cent), cystic fibrosis (3 per cent), tuberculosis (3 per cent), and aspiration syndrome (3 per cent). No predisposing illness could be demonstrated in 11 patients (15 per cent). In conclusion, approximately one-tenth of hospitalized children with pneumonia in our hospital had recurrent pneumonia. Most of these children had an underlying illness, which was demonstrated by intensive investigation. Bronchial asthma in children aged more than 2 years and gastroesophageal reflux in children aged less than 1 year were the most common underlying illnesses for recurrent pneumonia.