The goal of banding the pulmonary artery (PA) in children with complex heart disease is to reduce PA pressure and blood flow, relieve symptoms of circulatory congestion, and insure low pulmonary vascular resistance for future repair. To assess the hypothesis that two-dimensional echocardiography (E) measurements could be used to predict noninvasively the tightness of the PA band by measuring its diameter, we examined 15 patients with PA band. Of the 12 patients who underwent cardiac catheterization, nine with no symptoms of circulatory congestion had distal systolic PA pressure less than 0.5 systemic, and three symptomatic patients had distal PA pressure of more than 0.5 systemic. None had left ventricular outflow tract obstruction or pulmonary vascular disease. The E measurements were the internal diameter of the PA band (d), and PA annulus (D) in diastole. The d/D ratios correlated significantly with the ratios of measured distal to proximal PA systolic pressure (r = 0.98, P less than 0.001). Of the three patients not catheterized, one had a d/D ratio of less than or equal to 0.4 and two greater than 0.4. The former one had an excellent clinical improvement after banding, while the latter two remained in circulatory congestion. Doppler echocardiographic evaluation in five patients did not improve upon the data from the d/D ratios.(ABSTRACT TRUNCATED AT 250 WORDS)