Serial changes in patients with isolated VSD during adolescence have not previously been investigated. Hemodynamic status, diameter of the defect, and growth were studied yearly in 106 children with VSD. The mean duration of the follow-up was 13.16 years and ranged in 80% of subjects from 7 to 19 years (1395 patient years). The mean ages at pre-and postpuberty were 8.62 and 16.67, respectively. The presented longitudinal study, in which losses due to death and operation were minimal (4%), ideally reflected the natural history of VSD. Although weight showed retardation during prepuberty, this lag was caught up by the end of adolescence. Stature showed no retardation in pre-and postpuberty. Cardiothoracic ratio decreased significantly from a mean of 0.48 to 0.44 and showed normal variation. Although the mean defect diameter at prepuberty was 5.33 mm, this decreased to 2.7 postpubertally. The individual decrease (1.7 +/- 2.34, mm) was significant (t = 5.349, p < 1/10(5)). The defect closed spontaneously in 24 (22.6%). In the 75 patients without pulmonary hypertension and with mild left-to-right shunting, 52 remained in the same class and spontaneous closure was observed in 23. In the 24 patients with moderate to severe left-to-right shunt, this decreased in 23 and only one remained stable, The 2 patients (1.9%) with Eisenmenger syndrome remained stable and 1 died. Aortic regurgitution developed in 10 patients (9.4%); however, this was of mild degree in most of them. No infective endocarditis was observed. It is concluded that patients with VSD should be followed closely through adolescence, because the diameter of the defect, as well as left-to-right shunting, can decrease, and it is concluded that the spontaneous closure of the defect is to be expected in a considerable 23%, and aortic prolapse or mild regurgitation may develop in approximately 10%.