In order to standardize and quantify diagnostic information derived from medical histories and case reports given by demented patients, their families or care‐providers, a questionnaire has been developed containing 94 questions. The output is categorized by computer into graphic clinical scales which correlate and weigh information relating to seven of the most common causes of dementia. The present investigation assesses the validity of predictive diagnostic classifications derived from the clinical scales tested on admission by correlating them later with final diagnoses determined independently by thorough clinical evaluation including standard diagnostic tests, computed tomography and nuclear magnetic resonance scans. Results of 101 healthy, neurologically normal, age‐matched volunteers and 140 patients representative of the more common forms of dementia indicate that correct diagnostic identification was: 75% for dementia secondary to Parkinson's disease, 100% for Huntington's disease, 90.2% for Alzheimer's disease, 82.4% for multi‐infarct dementia, 90.0% for posttraumatic dementia, 77.8% for normal‐pressure hydrocephalus and 85.7% for Wernicke‐Korsakoff dementia. Correct diagnostic assignment was highly significant (P<.0005). The screening questionnaire may prove to be a useful and standard diagnostic tool for clinicians and investigators concerned with epidemiology, prevention and treatment of