Experience with transcatheter closure (TCC) of patent ductus arteriosus (PDA) in small infants is limited. Our goals were to evaluate the immediate and short-term results of TCC of PDA in small infants (< or = 8 kg) as attempted with single or multiple Gianturco coils and to compare results for PDA < or = 2.5 mm versus PDA > 2.5 mm. Twenty-four infants underwent an attempt at TCC of PDA at a median age of 0.7 years (range 2 weeks to 1.5 years) and median weight of 6.5 kg (range 2.3 to 8 kg). Coils were placed by the transvenous route in 14 patients and by the transarterial route in 10 patients. The median PDA diameter was 2.7 mm (range 0.4 to 5.2 mm). Ten patients had PDA diameters < 2.5 mm and all had complete closure, 9 with a single coil and 1 with two coils. Fourteen patients had PDA diameters > or = 2.5 mm; closure was complete in 10 patients, 9 of whom required multiple coils. There was a trend toward improved results with multiple coils delivered transvenously. There was immediate complete closure of the PDA with a diameter as large as 5.2 mm that persisted at a median follow-up period of 1.2 year. Closure was unsuccessful in 4 patients, each of whom required multiple coils. The median fluoroscopy time was 19 minutes. Complications included transient loss of femoral pulse in 2 infants, mild left pulmonary artery obstruction in 2, and nonretrievable coil migration to the right lung in one. We conclude that TCC is effective therapy for small infants with a PDA of diameter < or = 5.2 mm by the single-or multiple-coil technique on an outpatient basis and that TCC can be performed in neonates as small as 2.3 kg.