In order to assess the relative sensitivity and specificity of Katzman's short orientation memory concentration test (OMCT), 89 non demented patients and 44 patients affected by vascular or degenerative dementia were consecutively evaluated by three different mental status tests. The OMCT appeared equivalent to the Mini Mental State Examination in identifying dementia. Optimum sensitivity and specificity, respectively 88% and 94%, were achieved by a 10/11 cut-off score, giving a 11% false positive rate. Among patients with Alzheimer's disease, the OMCT score was correlated with mean values of a simple reaction time. It was also correlated with the Wechsler global MQ and the orientation, logical memory and paired associates items of the scale. There was no relationship between the OMCT score and the coloured Progressive Matrices IQ. The OMCT was reliable when given at 1 month interval. Serial evaluations did not show any significant practice effect.