Children after heart transplantation are considered as at-risk patients for extracardiac atherosclerotic complications. Noninvasive ultrasound measurement of the common carotid artery (IMT) provides valid information about the endothelial structure of the vascular system. Twenty-two patients (17 male, mean age 12.4 +/- 4.5 yr) after heart and (5.7 +/- 4.5 yr) heart-lung transplantation were enrolled. The mean IMT was measured and compared with a control group (18 children, 10 male, mean age 11.8 +/- 1.8 yr) and to normative data. Transplanted children had a higher IMT than controls (0.453 +/- 0.003 vs. 0.424 +/- 0.002 mm, p < 0.001). IMT-SDS was increased as well (1.6 +/- 0.1 vs. 0.8 +/- 0, p < 0.001). Transplanted children had a higher LDL/HDL-ratio (2.2 +/- 0.2 vs. 1.2 +/- 0.1, p < 0.001). Time after transplantation, age at the time of transplantation, or medical therapy did not influence the findings. We found evidence for subclinical atherosclerosis in children after heart and heart-lung transplantation. Even if single atherosclerotic risk factors could not be identified, transplanted children seem to be at risk for atherosclerosis. Our findings support the recently published statement of the AHA-Expert panel: after heart transplantation atherosclerotic complications may occur with increased incidence. We propose the IMT-measurement in these patients as an easy method to assess the vascular status and to guide preventive measures.