In the current study of 1062 Alzheimer's disease (AD) patients, we employed receiver operating characteristic curve analysis to identify characteristics of patients at increased risk for rapid cognitive decline. The patients are participants at one of the nine Alzheimer's Disease Research Centers of California. Rapid decline was defined as a 3-point or greater loss on the Mini-Mental State Examination (MMSE) per year, post visit. The independent variables were age at clinic visit, age at symptom onset of AD, MMSE at patient visit, years of education, gender, ethnicity, living arrangement, presence of aphasia, delusions, hallucinations, and extrapyramidal signs. Receiver operating characteristic curve analysis indicated that AD patients presenting with moderate to severe aphasia, age at clinic visit of 75 years or less, and an MMSE greater than 7 were at increased risk for rapid cognitive decline. This information could help clinicians target these patients for pharmacologic interventions, facilitate long-term care planning, and potentially create savings by delaying or stabilizing the course of the disease.