Objective To conduct a large population-based survey on multiple sclerosis (MS) prevalence in Shanghai,China.Methods We established a network of physicians,mainly neurologists,for identifying prevalent patients with MS and systematically checked inpatient registers at each hospital in the study area for patients with a diagnosis of MS,neuromyelitis optica,or other demyelinating disorders.MS diagnosis in patients was validated by senior neurologists according to the McDonald criteria.Results In total,123 patients with a validated MS diagnosis from the study population,8.86 million inhabitants with permanent residence in Shanghai,were alive on the prevalence day.The crude MS prevalence rate was 1.39 cases per 100 000 inhabitants (95% CI:1.16 to 1.66 cases) in the study population in Shanghai.There were 79 female and 44 male patients with MS,a female-to-male ratio of 1.8.Nearly all (96%) of the patients with validated MS had been examined by MRI.Conclusion Multiple sclerosis prevalence in Shanghai is in line with that reported for other Asian populations.