OBJECTIVES: To attach meaningfulness to clinically relevant differences on cognitive functioning using activities of daily living. METHODS: Baseline data from a 12-week clinical trial of patients with mild-to-moderate Alzheimer's disease (n = 212). Logistic regressions were used to examine the effect of the Mini Mental State Exam (MMSE) and, separately, the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog) on the Alzheimer's Disease Cooperative Study-Activity of Daily Living Inventory (ADCS-ADLI), after controlling for age and gender. A 3-point improvement on each of the two measures of cognitive function (MMSE and ADAS-cog) was taken a priori to be a clinically relevant difference between patients. Under that definition, an odds ratio (OR) of successfully performing each of 49 different activities of daily living was obtained. RESULTS: Subjects had a mean age of 75 years (SD = 8; range: 50-90) and were mostly white (92%) and female (58%). The Pearson correlation between ADAS-Cog and MMSE scores was -0.77 (p-value <0.01). A statistically significant association (p-value <0.05) existed between ADAS-Cog and 24 ADCS-ADLI items, and between MMSE and 22 ADCS-ADLI items. For these items, estimated odd ratios of performing an activity of daily living were 1.15 to 1.49 times more likely for every 3-point improvement in ADAS-Cog, and 1.3 to 2.3 times more likely for every 3-point improvement in MMSE. A 3-point improvement in ADAS-Cog (MMSE) reflected an average increase of 27% (62%) in the odds of performing activities of daily living. CONCLUSION: Linking clinically relevant differences on two common measures of cognitive functioning (MMSE and ADAS-cog) to activities of daily living can enhance the interpretation of these measures.