Since February 1990, we have attempted nonsurgical occlusion of persistent patency of the arterial duct using the Rashkind double-disk occluding device, of either 12 or 17 mm diameter. Results are presented from 31 patients (23 female and eight male, ages 15 months to 16 years). M-Mode, cross-sectional, Doppler and color Doppler echocardiographic studies were made prior to closure, in the following 24 hours, and six months later. Left ventricular diastolic dimension and shortening fraction, systolic intervals, and left atrium/aortic ratio were evaluated by M-Mode echo. We examined carefully the location of the device relative to the left pulmonary artery and descending aorta, also checking for disturbed flows and residual shunts. These studies showed a clear tendency for the left ventricular diameter to decrease, and revealed a significant normalization of the left atrium/aortic ratio. Successful closure of the duct was achieved in 27 cases. Follow-up studies six months later showed residual shunting in four cases. In one patient, a second device was implanted with an excellent result. At the immediate follow-up, turbulences were noted in the area of the device (nine cases) and in the left pulmonary artery (seven cases). Distortion of the anatomic orientation of the left pulmonary artery was observed in three cases in which we discovered 20 mm Hg systolic gradients. In our opinion, echocardiography is the best technique with which to follow-up these patients. The high sensitivity of color Doppler echocardiography revealed minimal distortion of the left pulmonary artery, probably generated by regional anatomic adjustment to the insertion of the device.