Objective: To summarize the characteristics of Chinese clinically isolated syndrome (CIS) patients and their 3-year follow-up results. Investigate the relationship between CIS features and clinical outcomes. Methods: Forty-nine CIS patients were recruited and 42 of them were able to be followed up for a mean of 38 months (range 26-48 months). We recorded baseline features including patient demographics, site of CIS, presence or absence of cerebrospinal fluid (CSF) oligoclonal bands (OCB) and MRI lesions in brain and spinal cord. The incidence of conversion to clinically definite MS (CDMS) or neuromyelitis optica (NMO) after CIS was calculated, and the relationship between baseline features and CDMS was explored. All data were statistically processed with SPSS for Windows Version 11.5. Results: After a mean follow-up of 38 months, 10/42 patients had converted to CDMS (24%), and one patient had developed definite NMO. The other 31 patients remained in CIS status. A spinal cord syndrome was the initial CIS manifestation in 57% of patients. The conversion rates to MS were 22% (5/23) for patients presenting with a spinal cord syndrome and 27% (3/11) for multi-focal manifestations. The three-year CDMS conversion rates were 70% (7/10) for patients who fulfilled the MRI dissemination in space criteria (2005 revised McDonald) at onset of CIS, while only 9% (3/32) of patients who did not fulfill these criteria converted to CDMS. Females had significantly higher conversion rate than males. Conclusion: A spinal cord syndrome was the most common initial presentation of our Chinese CIS group. After a mean follow-up of 38 months, the conversion rate to MS was approximately 25%. The 2005 revised McDonald MRI criteria for dissemination in space is a key prognostic factor for conversion to MS in CIS in Chinese patients. (C) 2011 Elsevier B.V. All rights reserved.