OBJECTIVES: Evaluate the psychometric properties of the revised version of the Medical Outcomes Study Cognitive Functioning Scale (MOS-Cog-R) using data from a representative sample of U.S. adults.  METHODS: The 6-item MOS-Cog yields a single score representing impairment across a range of cognitive functions, including memory, reasoning, attention/concentration, and confusion, over the previous four weeks.  The MOS-Cog-R introduced several changes: one response option was removed; a one-week recall period form was introduced; and 0-100 scoring was replaced by norm-based T-scores (mean=50, standard deviation=10), standardized using data from a 2009 U.S. internet-based general population normative survey to improve interpretability.  The psychometric properties of both one-week (acute) and four-week (standard) recall forms of the MOS-Cog-R were examined within the development sample.  Scale reliability was evaluated using inter-item correlations and Cronbach’s alpha.  Construct validity was tested using correlations with relevant continuous criterion variables and analysis of covariance models comparing mean MOS-Cog-R scores across levels of categorical criterion variables.   RESULTS: Acute and standard forms of the MOS-Cog-R were completed by 2012 and 2003 respondents, respectively.  Both forms showed adequate internal consistency reliability (all inter-item correlations>0.40; both Cronbach's alphas≥0.89). MOS-Cog-R scores showed greater correspondence with mental domains of quality of life than physical domains (e.g., correlations for both forms with SF-12v2 mental and physical summary scores were ≥0.55 and ≤0.28, respectively).  Direction and magnitude of correlations with criterion measures of psychological status (e.g., depression, anxiety) and health outcomes indicated good convergent validity for both forms.  Differences in mean scores across respondents stratified by criterion outcomes supported adequate discriminant validity of each form.     CONCLUSIONS: The MOS-Cog-R introduces a number of improvements, including simplified responses, the introduction of a one-week recall form, and norm-based scoring that enhances interpretability of scores.  Both acute and standard recall-period forms of the MOS-Cog-R demonstrated good reliability and validity.