BACKGROUND Transcatheter occlusion with Gianturco coils has been attempted in a small number of patients with tiny (< or = 1.5-mm diameter) patent ductus arteriosus, and preliminary results have been encouraging. The present study extends this method to larger ductus sizes and makes recommendations for proper coil size selection. RESULTS Coil occlusion was attempted in 24 consecutive patients with patent ductus arteriosus who did not require other cardiac surgery. Median patient age was 4.2 years (8 months to 30 years), and mean ductus diameter was 1.7 +/- 0.8 mm. Two instances of coil embolization occurred in the first 4 patients, with successful coil retrieval. Based on this experience, we proposed that the coil helical diameter should be twice or more the minimum ductus diameter, with coil length sufficient for three or more loops. With these recommendations, coils were successfully implanted in the subsequent 20 consecutive patients. Of the 22 patients with successful coil implantation, 15 (68%) had no residual shunting, and 7 had trace residual shunting by angiography. The continuous murmur was abolished in all 22 patients. No significant complications occurred, and all patients were discharged within 24 hours of successful coil implantation. No change in the systolic pressure gradient between main and left pulmonary artery or ascending and descending aorta was observed. CONCLUSIONS Transcatheter occlusion of patent ductus arteriosus can be safely and effectively achieved in patients with ductus diameters up to 3.3 mm. Coil occlusion does not cause obstruction to flow in the left pulmonary artery or descending aorta. Coils should be selected to provide a helical diameter twice or more the minimum ductus diameter and a length sufficient for three or more loops.