OBJECTIVES: To investigate the effect of chronic diseases and disease combinations on 1-year mortality in nursing home residents. DESIGN: Retrospective cohort study using electronically submitted Minimum Data Set (MDS) information and Missouri death certificate data. SETTING: Five hundred twenty-two nursing homes in Missouri. PARTICIPANTS: Forty-three thousand five hundred ten nursing home residents with a full MDS assessment in 1999. MEASUREMENTS: Information about chronic diseases, age, sex, and performance in activities of daily living (ADLs) available from the first full MDS 2.0 assessment in 1999; death within 1 year after the first full MDS-assessment in 1999. RESULTS: After adjustment for age and sex, eight variables were predictive for 1-year mortality: seven chronic diseases (dementia, cancer, heart failure, renal failure, emphysema/chronic obstructive pulmonary disease, diabetes mellitus, and anemia) and an interaction variable containing age and cancer. Adding terms for disease combinations (e.g., diabetes mellitus and heart failure) did not enhance survival prediction. When there was also adjustment for ADL performance as measured using the MDS-ADL Short Form, dementia and anemia were not included, because they had no prognostic value above that of the other variables. CONCLUSION: Several chronic diseases were associated with 1-year mortality in the institutionalized elderly after adjustment for ADL performance, age, and sex. Evidence of a synergistic effect of disease combinations on mortality is lacking. © 2005 by the American Geriatrics Society.