Ideomotor apraxia is one of the earliest disturbances in Alzheimer's disease (AD); no test of this disturbance has yet been validated for elderly people. We propose a test of meaningless gesture imitation and its relevance in elderly people is studied. The Ideomotor Apraxia Test (IAT) consists of showing 10 gestures. Each item is graded from 0 to 3. IAT was carried out on 55 patients with AD (mean age: 86.8 +/- 6.8 (71-100); mean MMS score: 14.6 +/- 6.3) and 26 elderly patients without cognitive impairment (mean age: 84.1 +/- 7.5 (70-100); mean MMS score: 27.5 +/- 1.9). The inter-rater reliability, a threshold, the apparent sensitivity and specificity and the relationship between the MMS score and the ideomotor apraxia score were determined. The mean apraxia score was 14.9 +/- 7.3 in the AD group and 28 +/- 1.6 in the normal group (P < 0.0001). Inter-rater agreement is excellent (P = 0.995). The threshold is 27. The apparent sensitivity and specificity are very good (95% and 88%, respectively). The correlation between the MMS score and ideomotor apraxia score is excellent (r = 0.83 (95% CI; 0.72-0.91). Age and educational level do not influence ideomotor apraxia score. IAT is the first test that evaluates meaningless gesture imitating capacity in an elderly population. It is an easy and quick-to-perform test, useful routinely for diagnosis of AD. It could contribute to the early diagnosis of AD and is correlated with the severity of cognitive impairment. Copyright 1998 Lippincott Williams & Wilkins