Several studies have reported an association between aggression and cholesterol levels. The purpose of this study was to investigate the relationship of serum cholesterol and triglyceride levels with aggression and cognitive function in elderly inpatients. One hundred ten patients consecutively admitted to the Geriatric Psychiatry inpatient unit at Houston's Veterans Affairs Hospital received comprehensive evaluations by a multidisciplinary team. Fasting serum cholesterol and triglyceride levels were obtained within 3 days of admission. In addition, two geriatric psychiatrists administered the Mini-Mental State Examination (MMSE) and the Cohen-Mansfield Agitation Inventory (CMAI). Correlation coefficients were calculated between lipid levels, CMAI total and subscale scores, and MMSE scores. Multiple linear-regression analyses were done to further investigate the relation between lipid concentrations and various confounders. We found no significant correlation between serum triglyceride levels and MMSE, CMAI total, and CMAI factor scores. In addition, we found a significant positive correlation between serum cholesterol levels and physical nonaggressive behavior, and a significant negative correlation between serum cholesterol levels and MMSE scores. We found no relationship between aggressive behavior and serum cholesterol or triglyceride levels. However, an association between high cholesterol levels and agitation exists, which may be mediated by the association between high cholesterol levels and impaired cognition.