To develop a total or composite score for the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) neuropsychological battery. CERAD total scores were obtained by summing scores from the individual CERAD subtests (excluding the Mini-Mental State Examination [MMSE]) into a total composite (maximum score = 100). The method of tabulating the total score was constructed using normal controls (NCs; n = 424) and patients with AD (n = 835) from the CERAD registry database. The utility of the total score was further tested in independent samples of mild AD (n = 95), mild cognitive impairment (MCI; n = 60), and NC (n = 95) subjects. The CERAD total score was highly accurate in differentiating NC and AD subjects in the CERAD registry. Age, gender, and education effects were observed, and demographic correction scores were derived through multiple regression analysis. Demographically corrected CERAD total scores showed excellent test-retest reliability across samples (r = 0.95) and were highly correlated with the MMSE (r = 0.89) and Clinical Dementia Rating Scale (r = -0.83) in mixed AD and NC samples and with the Blessed Dementia Rating Scale in an AD sample (r = -0.40). The CERAD total score was highly accurate in differentiating independent samples of NC, MCI, and AD subjects. Results provide support for the validity of a Consortium to Establish a Registry for Alzheimer's Disease (CERAD) total score that can be used along with the normative data to provide an index of overall level of cognitive functioning from the CERAD neuropsychological battery.