Background: Proadrenomedullin N-terminal 20 peptide (PAMP) is a novel hypotensive peptide present in the precursor of adrenomedullin (AM), a vasodilative and natriuretic peptide. However, the profile of PAMP in hemodialyzed (HD) patients has not been determined. Methods: We measured plasma levels of PAMP, total AM (tAM) and a mature form of AM (mAM, the biologically active form) in HD patients (n = 31) and in normal controls (n = 21). Results: Plasma concentrations of PAMP before HD were significantly higher than those in controls (4.02 ± 0.24 vs. 1.64 ± 0.12 fmol/ml, p < 0.001) and decreased to the control level after HD (2.17 ± 0.18 vs. 1.64 ± 0.12 fmol/ml; NS). The plasma PAMP level before HD significantly correlated with weight gain during HD sessions (r = 0.41, p < 0.05), but not with predialysis blood pressure. The concentrations of mAM before and after HD were significantly higher than those in controls. The plasma mAM level before HD significantly correlated with weight gain during HD sessions, but not with predialysis blood pressure. The plasma level of PAMP did not correlate with that of mAM in HD patients. Conclusion: PAMP and AM may be involved in the regulation of blood volume in patients undergoing HD.