To characterize the determinants of circulating levels of adrenomedullin (AM), the plasma levels of this peptide were measured in 58 patients with end-stage renal disease on hemodialysis. Predialysis plasma levels of AM were more than twice as high in patients on hemodialysis as compared to controls. In hemodialysis patients with heart failure (NYHA classes II–IV) or hypertensive HD patients plasma levels of AM were significantly higher than in patients with end-stage renal disease only. Plasma levels of AM were not altered immediately by hemodialysis but decreased significantly 14–20 h after hemodialysis. AM plasma levels before hemodialysis and 14–20 h after hemodialysis were correlated with the corresponding mean arterial pressure.