Recent years have witnessed increased interest in the Clock-Drawing Test as a simple and reliable method of early detection of disturbed cognitive functioning in the elderly. Four versions of the test are presented, two proposed by Shulman et al. and those proposed by Sunderland et al. and Watson et al. All versions of the Clock-Drawing Test combine simplicity with high sensitivity and specificity with respect to diagnosis of disturbed cognitive efficiency. This test seems particularly useful as a selective diagnostic instrument for disturbed cognitive efficiency associated with the early stages of Alzheimer's disease when general cognitive efficiency has not yet reached the level of dementia.