PURPOSE: This study examines the association between socioeconomic status and cognitive decline in a community-based cohort of well-functioning older adults and seeks to determine whether this link could be explained by biomedical factors. METHODS: Data are from 2574 men and women aged 70 to 79 years from Pittsburgh, PA, and Memphis, TN, participating in the Health, Aging and Body Composition study (Health ABC). Three indicators of socioeconomic status were used: education, income, and ownership of financial assets. Cognitive decline over 4 years was defined as a decrease of five points or more in the Modified Mini-Mental State Examination (3MS) score. Biomedical factors measured at baseline, included heart disease, cerebrovascular disease, diabetes, hypertension, poor pulmonary function, and high serum levels of inflammatory markers. RESULTS: Adjusted odds ratios were significantly higher in those with low education, low income, and few assets. Odds ratios ranged from 1.51 to 2.16 in the lowest socioeconomic groups. Additional adjustment for biomedical factors reduced the odds ratios of cognitive decline by an average of 2% for education, 5% for income, and 8% for the number of assets. CONCLUSIONS: Low socioeconomic status predicts a decline in cognitive function in older adults and this relationship is not mediated by biomedical factors. © 2005 Elsevier Inc. All rights reserved.