This study was designed to examine the utility of the ADAS-Cog, Chinese version (ADAS-Cog-C) for staging of dementia in Alzheimer disease (AD). A total of 305 patients with AD (199 mild AD and 106 moderate AD) meeting the NINCDS-ADRDA criteria of probable AD were recruited. The ADAS-Cog-C was administered to all AD subjects. The total score of ADAS-Cog-C and each item score differed significantly between mild and moderate AD groups, with moderate AD group scoring higher. Statistical analysis showed insignificant influence of age or educational level on the ADAS-Cog-C total score. The item score of orientation and constructional praxis and the ADAS-Cog total score could classify mild and moderate AD efficiently, with a sensitivity of 78% to 82% and a specificity of 70% to 73%. The results of this study indicate that the ADAS-Cog-C can discriminate mild AD from moderate AD efficiently and be useful for staging of AD. It is recommended that the ADAS-Cog-C be introduced for monitoring the cognitive efficacy in AD drug treatment among Chinese AD patients.