Adrenomedullin (ADM) is a vasoactive and natriuretic peptide. While it is known that ADM is increased in failing human ventricles, the expression of ADM in human ventricular allografts remains unknown. The present study was designed to investigate tissue localization and intensity of ADM expression in ventricular biopsy specimens and to characterize ventricular ADM in human cardiac allografts. Thirty-three post-transplant endomyocardial biopsy specimens were examined immunohistochemically. The average score (range: 0-4) of ADM immunoreactivity (IR) was 2.4±0.9 (mean±standard deviation). Right ventricular (RV) systolic pressure was significantly increased with high ADM-IR (p=0.048) and the ADM-IR positively associated with myocyte size (r2=0.23, p=0.010). In contrast, ADM-IR was not associated with systemic blood pressure, serum creatinine, cyclosporine concentration, cardiac fibrosis, or allograft rejection. The present study shows that ADM-IR is present in human ventricular endomyocardium after transplantation, and ADM-IR is associated with the magnitude of RV pressure and myocyte size, suggesting an important role for ventricular ADM in the counteraction against overload as well as in the progress of myocyte hypertrophy after heart transplantation. © 2003 Elsevier Science B.V. All rights reserved.