Late complications in pediatric cardiac transplant recipients. Late complications occurring more than 3 months after cardiac transplantation were analyzed in 29 pediatric patients in whom 31 cardiac transplantations were performed. Age at transplantation ranged from 3 months to 18 years (mean, 11.3 years) with follow-up ranging from 3.5 to 54 months (mean, 21.6 months). There were seven late deaths and two patients with retransplantations. Of nine grafts lost, eight were due to acute rejection, and one was due to coronary disease. Four of the grafts lost were secondary to patient noncompliance with prescribed immunosuppression. The mean rejection frequency more than 1 year after cardiac transplantation was significantly higher in those patients who eventually lost their grafts; however, these patients could not be distinguished by their rejection frequency in the first year. Eight patients had coronary disease, with five diagnosed at autopsy, two at cardiac retransplantation, and one by angiography. All eight patients were on double immunosuppression; none of the 19 patients on triple therapy had coronary disease with similar follow-up. There were 12 serious infections in eight patients (four associated with OKT3) with no deaths. Five patients had arrhythmias requiring treatment including two pacemakers; four of the five were associated with rejection episodes. Twelve of 29 patients developed early hypertension, and five developed late hypertension (greater than 1 year). There were two malignancies; one patient with Hodgkin's lymphoma was cured with chemotherapy, and one patient with histiocytic lymphoma was discovered at autopsy. Two patients had cholecystectomies, and five patients required laser gingivectomies. 