OBJECTIVE: To assess the effectiveness of modified, controlled release Gianturco coils for transcatheter occlusion of the arterial duct. DESIGN: Prospective study, approved by local medical ethics committee. SETTING: Tertiary paediatric cardiac centre. PATIENTS: 43 patients with left to right shunting through the arterial duct, two of whom had a residual leak after surgical ligation and three had residual shunting after previous Rashkind umbrella implantation. INTERVENTION: Transcatheter delivery of one or more coils to the arterial duct. MAIN OUTCOME MEASURES: Complete occlusion of the arterial duct, based on intention to treat and judged by Doppler echocardiography. Absence of flow disturbance in the branch pulmonary arteries and the descending aorta following the procedure. Assessment of cost of the disposable items used. RESULTS: At a median follow up period of three months complete duct occlusion was achieved in 37 (86%) of the 43 patients. No flow disturbance in the branch pulmonary arteries or the descending aorta was detected in any patient. The median cost of disposable items used during the procedure was 342 pounds. CONCLUSIONS: The Cook detachable coil is an effective and financially attractive alternative to the Rashkind umbrella for closure of the arterial duct.