AIM: To determine the natural history and timing of spontaneous closure of ventricular septal defect (VSD) in patients followed from less than six months of age in our cardiac clinic. METHODS: Using color Doppler flow mapping, a total of 84 infants were diagnosed of isolated VSD: 41 (48.8%) muscular type, 33 (39.3%) perimembranous, 7 (8.3%) subpulmonary, and 3 (3.6%) mal-aligned. The patients were divided into two groups. Sixty-four patients were diagnosed at the age of less than or equal to one month (group I) and 20 were diagnosed at the age of more then one month (group II). Spontaneous closure of VSD was confirmed by color Doppler flow mapping. RESULTS: Surgical closure was performed in four patients (4.8%). Spontaneous closure occurred in 52 patients (61.9%) of the whole group, 73.4% of group I and 25 % of group II, respectively. Spontaneous closure occurred only in patients with perimembranous type of VSD (48.5%; 16/33) and in patients with muscular type (87.8%; 36/41). None of the subpulmonary or mal-aligned types of VSD closed spontaneously. CONCLUSIONS: Muscular type VSD was the most common type of VSD in group of very young infants. Spontaneous closure of VSD is age-dependent, occurring mainly in muscular and perimembranous types of VSD.