〔Abstract〕 Objective To examine the relationship between the levels of endothelin-1(ET-1) and the severity of clinical symptoms in idiopathic inflammatory demyelinating diseases(IIDDs) of the central nervous system. Methods A total of 45 patients with central nervous system demyelinating diseases were enrolled in the study. Among them, 25 patients were diagnosed with idiopathic IIDDs, 20 had vascular demyelinating diseases of the central nervous system, and 10 healthy controls were also included. Serum ET-1 levels were assessed using ELISA, and a further analysis was conducted to investigate the correlation between these ET-1 levels, laboratory test results, and the degree of disease disability in the IIDDs patient group. Results(1) Of the three groups, ET-1 levels were highest in the IIDDs(Ps=0.503, P=0.010), CSF total protein(rs=0.475, P=0.016), CSF albumin(rs=0.480, P=0.020), CSF IgG(rs=0.544, P=0.007), IgA(rs=0.660, P=0.002) and IgM(rs=0.555, P=0.011) levels.(3) There was a positive correlation between serum ET-1 levels and CSF IgM levels(rs=0.455, P=0.044) in IIDDs group. Serum ET-1 level showed no significant correlation with peripheral immune reaction(P>0.05). Conclusion Serum ET-1 levels reflect the severity of clinical symptoms in IIDDs and show no significant correlation with peripheral immune markers, however, exhibit a positive correlation with disease severity and cerebrospinal fluid IgM levels. These findings suggest that serum ET-1 levels may indicate the degree of central nervous system inflammation and play an important role in the development and progression of IIDDs.