In a preadmission domiciliary study of 230 patients presented to a medical geriatric service (physical illness and physical disability predominating) intellectual deterioration was identified and quantified by means of simple arithmetical calculations, digit span forwards and reverse, interpretation of proverb, the mental status questionnaire (M.S.Q.), and the physician's overall assessment. Statistical analysis showed that the power of discrimination of the M.S.Q. was greater than that of any of the other individual tests; and that there seemed to be no advantage in adding one or more of the other tests to the M.S.Q. This brief and simple verbal test can generally be given without causing fatigue, anxiety, or embarrassment, even to the seriously ill and disabled. Its routine use in practice with elderly patients is recommended.