Abstract: Objective: To investigate the expression of adrenomedullin(ADM) in human lung cancer and to evaluate its clinical significance.Methods: Immunohistochemical staining was performed to examine the expression of ADM in lung cancer,radioimmunoassay was applied to determine the concentration of ADM in the plasm of patients and controls,and the relationship was retrospectively analyzed between the expression of ADM in lung cancer and the clinicobiological features.Results: The expression of ADM in lung cancer was significantly higher than those in adjacent tissues and normal tissues(P<0.01),and the positive rate of ADM protein in adjacent tissues and that in the normal ones was no significant difference(P>0.05).There was a significant relationship between the expression of ADM and the grade of lung cancer(P<0.05 and P<0.01),and there were no relationships between the expression of ADM and age,histological type and TNM stage(P>0.05).The expression of ADM in the plasm of lung cancer group was significantly higher than those in the plasm of non-lung cancer group and healthy control group(P<0.05).There was a significant relationship between the expression of ADM in the plasm and TNM stage(P<0.05),and there was no relationships between the expression of ADM in the plasm and histological type(P>0.05).Conclusions: The expression of ADM significantly increased in lung cancer and was associated with grade.ADM may play an important role in the lung cancer.