The Richardson classification system for aortopulmonary septal defect (APSD) includes simple defects between the ascending aorta and pulmonary trunk (type I), defects extending distally to include the origin of the right main pulmonary artery (type II), and anomalous origin of the right main pulmonary artery from the ascending aorta with no other aortopulmonary communication (type III). These are rare lesions that must be repaired in early infancy to avoid development of pulmonary vascular disease. Few reports have focused on patients with complex, associated lesions who underwent repair in early infancy. Between 1972 and 1995, 24 patients with Richardson type I (n = 11), II (n = 7), or III (n = 6) defects underwent repair at ages ranging from 2 to 172 days (median 34). Twelve patients had complex, associated anomalies, including interrupted or hypoplastic arch (n = 9), tetralogy of Fallot with (n = 1) or without (n = 1) pulmonary atresia, and transposition of the great arteries (n = 1). The most recent 7 patients were diagnosed by echocardiography without cardiac catheterization. There were no early or late deaths among the 12 patients with simple APSD. Four patients with complex, associated lesions died in the early postoperative period and another died 4 months after surgery. All 6 surviving patients with interrupted arch have had recurrent obstruction at the arch repair site, although reintervention for this reason has been performed in only 2 patients. Altogether, 6 early survivors have required reintervention, and all survivors are in New York Heart Association class I at follow-up ranging from 2 to 25 years. Thus, long-term survival after repair of APSD in early infancy is excellent. Late sequelae are likely to be related either to associated lesions or to obstruction at the APSD repair site. Almost all cases of APSD in young infants can be diagnosed and evaluated by echocardiography without catheterization.