Twenty-seven children with pulmonary valvar stenosis with pressure gradient (PG) > or = 40 mmHg underwent percutaneous balloon pulmonary valvuloplasty (PBPV) at Siriraj Hospital between February 1993 and August 1996. There were 13 males and 14 females, with an age range from 2 months to 14 years, and body weight from 4.7 to 42.1 kg. The majority (92.6%) were asymptomatic. Before the PBPV, the pulmonary valve annulus (PVA) measured by echocardiography was significantly greater than that measured by cardiac catheterization (15.2 +/- 3.7 vs 14.5 +/- 3.9 mm, P = 0.006). However, there was linear association (r = 0.972) between the two methods. The PG obtained by the two methods showed no significant difference (90.8 +/- 35.3 by echocardiography vs 97.3 +/- 47.2 mmHg by catheterization, P = 0.266). Immediately after PBPV, the right ventricular systolic pressure (113.7 +/- 41.1 pre vs 62.3 +/- 28.1 mmHg post) and the PG 103.4 +/- 43.4 pre vs 49.0 +/- 31.1 mmHg post) were significantly reduced (p < or = 0.0005). At 6-mo follow-up echocardiography, the PG was 28.6 +/- 17.6 mmHg and was significantly reduced (P = 0.0005). The PVA significantly increased at the 12 mo follow-up (15.2 +/- 3.6 pre vs 17.6 +/- 3.8 mm post, P = 0.001). Only minor complications were reported in the present study; bleeding (3.7%), transient bradycardia (7.4%) and pulmonary regurgitation not more than moderate severity (79%). The immediate and intermediate results of PBPV are excellent with a success rate of 85 per cent.