A model of risk potential for developmental outcome was created based on cardiac, medical, surgical, and family-stress factors in 31 children with transposition of the great arteries who had undergone reparative open heart surgery utilizing cardiopulmonary bypass during infancy. Impact of these potential risk factors was assessed by 4 current neurologic measures (neurologic anatomic abnormalities, functional impairment, electroencephalograph [EEG], and Pattern Visual Evoked Potential [PVEP]) and 4 psychologic measures (IQ, achievement, perceptual-motor function, and behavior). Results indicated that adverse developmental outcome was significantly associated with the following medical risk variables: failure of palliative surgery to alleviate hypoxia, prolonged hypoxia, growth failure, congestive heart failure, absence of ameliorating shunting heart defects, stroke, and CNS infection; and two psychosocial moderator variables: socioeconomic status and current life stress. Analysis of a "cumulative risk score" indicated significantly higher risk scores in children with abnormal EEGs, PVEPs, and neurologic examinations. The cumulative risk score highly correlated with composite neurologic outcome (r = .62), IQ (r = -.66), achievement (r = -.60), and perceptual-motor function (r = -.48). While overall outcome was favorable for children with TGA who experienced a single risk event, outcome was compromised if multiple risk factors occurred.