OBJECTIVES: To determine the incidence and correlates of combined declines in cognitive and physical performance. DESIGN: Cohort study of community-dwelling older women with moderate to severe disability. SETTING: The community surrounding Baltimore, Maryland. PARTICIPANTS: Participants in the Women's Health and Aging Study I with Mini-Mental State Examination (MMSE) score or 24 or greater and walking speed greater than 0.4 m/s at baseline. MEASUREMENTS: Cognitive decline was defined as an MMSE score less than 24 and physical decline as a walking speed of 0.4 m/s or less in at least one of the three annual follow-up visits. Participants were stratified into groups based on cognitive or physical decline or both. Group characteristics were compared, and results were adjusted for age, race, education, and significant covariates. RESULTS: Of 558 women that met the baseline MMSE and walking speed inclusion criteria, 21% developed physical decline, 12% developed cognitive decline, and 11% experienced combined cognitive and physical decline. After adjustment, physical decline was associated with age, non-white race, former smoking, baseline walking speed, and instrumental activities of daily living (IADL) impairment. Cognitive decline was associated with age and baseline MMSE score. Combined decline was associated with age, baseline walking speed, MMSE score, IADL impairment, as well as current smoking (odds ratio (OR) = 5.66, 95% confidence interval (CI) = 1.49-21.54) and hemoglobin level (OR = 0.68, 95% CI = 0.47-0.98). CONCLUSION: Potential predictors of cognitive and physical performance decline were identified. The association between smoking and lower hemoglobin levels and combined cognitive and physical decline may represent potentially modifiable risk factors and should be confirmed in future studies.