Case series Patients: Male, 71-year-old • Male, 56-year-old • Male, 61-year-old • Male, 74-year-old Final Diagnosis: Dementia with Lewy bodies Symptoms: Psychosis Clinical Procedure: — Specialty: Geriatrics Objective: Unusual or unexpected effect of treatment Background: Many patients with dementia with Lewy bodies (DLB) experience cholinesterase inhibitor- and antipsychotic-resistant psychosis. The new second-generation antipsychotic pimavanserin has been used with some success in the treatment of psychosis in other forms of dementia, including Alzheimer disease and Parkinson disease dementia. It is possible that pimavanserin may also be useful in the treatment of psychosis in DLB. We sought to describe the disease course and treatment of psychosis in 4 patients with DLB who were prescribed pimavanserin after other medications failed to reduce the frequency or severity of hallucinations and delusions. Case Report: This is a case series of 4 male patients (ages 56 to 74 at the beginning of the reports) who developed DLB and psychosis (eg, visual illusions, visual and olfactory hallucinations, and paranoid delusions). All 4 patients were prescribed cholinesterase inhibitors (eg, donepezil or rivastigmine) prior to pimavanserin, and only 1 patient experienced improved psychosis while on cholinesterase inhibitors. All 3 patients who were prescribed first-generation antipsychotics (eg, haloperidol) or traditional second-generation antipsychotics (eg, olanzapine, risperidone, or quetiapine) experienced initial or lasting side effects with no improvement of psychosis. Conversely, all 4 patients tolerated pimavanserin well, and 3 of the 4 patients experienced significant improvement of psychosis (eg, fewer hallucinations, fewer delusions, reduced paranoia, and/or reduced distress or agitation related to hallucinations and delusions) when prescribed pimavanserin. Conclusions: This case series suggests that pimavanserin is tolerable in older males with DLB and that it may be useful for the reduction of distressful hallucinations, delusions, and paranoia in patients with DLB.