Coronary intravascular ultrasound imaging has been found to be the most sensitive method for detecting postcardiac transplantation coronary vasculopathy. Techniques for this type of imaging have been well established for adult patients, but coronary intravascular ultrasound imaging in young children has not been previously reported. We describe the cases of 2 children, ages 8.5 years and 9 months, respectively, who had confusing clinical pictures after cardiac transplantation. Currently available imaging equipment and techniques were used in these children to visualize the coronary arteries. The results of ultrasound imaging were considered helpful in determining future treatment for these 2 pediatric patients.