Background Psychotic symptoms and behavioral disturbances are a leading cause of institutionalization in elderly patients with Alzheimer's disease (AD). Objectives Elderly nursing home patients (n = 105) with possible or probable AD Acre entered into a multicenter study to determine the long-term efficacy and safety of olanzapine in treatment of psychotic symptoms and behavioral disturbances due to AD. Methods Following a double-blind, 6-week exposure to fixed-dose olanzapine (5, In, or 15 mg/d), patients entered an additional 18-week, open-label, flexible-dose treatment. Baseline was defined from the start of the extension phase. Results Patients improved significantly on the primary efficacy measure, defined a priori, which consisted of the sum of the Agitation/Aggression, Delusions, and Hallucinations items ('Core') of the NPI/NH. Olanzapine also significantly improved score, for the NPI/NH total and the Core item-associated Occupational Disruptiveness of the NPI/NH, as well as the BPRS total and CGI Severity-of-Alzheimer's scores. Barnes Akathasia scores improved significantly from baseline, while Simpson-Angus and AIMS scores were not significantly changed. Treatment-emergent symptoms included somnolence, accidental injury, and rash. No significant changes were seen in ECGs, including QT(c) internal, nor in weight or vital signs, including orthostasis. Conclusions Low-dose olanzapine appears to be effective and well tolerated for treatment of behavioral disturbances and psychotic symptoms due to AD in elderly patients. Copyright (C) 2001 John Wiley Sons, Ltd.