Background Accelerated coronary atherosclerosis after heart transplantation (TCAD) is a major cause of late death.It is progressive and eventually fatal, and currently no therapy exists. The purpose of this study was to determine the incidence as well as the clinical and age-dependent characteristics of pediatric patients with TCAD.Methods and Results Pediatric heart transplantation centers were surveyed on patient outcome and incidence of TCAD from August 1974 to March 1993.A follow-up questionnaire was sent to examine patient-specific details, including age at transplantation and at death, time to diagnosis, and rejection history. Data on coronary angiography and autopsy findings were requested. Replies were received from 17 US centers that performed 815 pediatric heart transplantations (including 188 neonates), with 560 survivors (69%). TCAD was identified in 58 patients (7.3%) by either coronary angiography, autopsy, or both. Detailed data were available for 45 patients. The mean age at diagnosis of TCAD was 9.9 years (0.2 to 26 years), and mean posttransplantation time was 2.2 years (0.1 to 7.7 years). TCAD occurred in 16 patients who received transplants before age 2 years. Many deaths were sudden and unexpected. Only 9 of 58 patients are alive, including 5 who had a second transplant. Four or more treated cellular rejection episodes and one or more courses of monoclonal antibody were used in 60% of patients with TCAD. Angiography was performed in 45 and was normal in 15 patients who later died of TCAD. An autopsy, performed in 36 of the 49 who died, showed severe coronary stenosis in 28 (78%) and concurrent cellular rejection in 26 (72%).Conclusions TCAD is a serious problem in transplant recipients and may affect patients of any age, even neonates.Diagnosis is difficult, and incidence of TCAD may be underestimated. TCAD appears to be associated with cellular rejection; thus, higher surveillance in patients with frequent rejection episodes is indicated. Better surveillance methods, such as intravascular ultrasound and quantitative analysis of angiographic data, are needed to improve detection and assess new treatment strategies. (Circulation. 1994;90(part 2):II-56-II-60.)