Emerging evidence suggests that psychosis in persons with Alzheimer's disease (AD) may be linked to the cholinergic deficit associated with the disease. This study sought to evaluate whether anticholinergic (ACH) drugs could be a risk factor for psychosis onset. A total of 230 patients affected with probable AD were recruited. Data on behavioral and psychological symptoms were collected using the Neuropsychiatric Inventory, and diagnosis of psychosis was performed. Patients were divided into those who used ACH drugs and those who used non-ACH drugs. Those using ACH drugs (18.3%) were more likely to have psychosis than those using non-ACH drugs (odds ratio (OR)=2.52; 95% confidence interval (CI), 1.27-5.00); this association remained significant even after adjusting for potential confounding variables (OR=2.13; 95% CI, 1.03-4.43). Our data suggest that patients with AD are frequently treated with ACH drugs and that ACH drug intake should be regarded as a potential risk factor for psychosis.