Psychosis is a common problem in advancing Parkinson disease (PD). There are significant limitations of standard approaches of adjusting dopamine replacement therapies and using unconventional anti-psychotic agents such as clozapine and quetiapine. Pimavanserin is a promising addition to our therapeutic arsenal. Hawkins and Berman thoughtfully emphasize our relatively limited knowledge of pimavanserin clinical pharmacology. It was approved on the basis on 1 trial in a selected group of PD participants. Additional trials, particularly in PD dementia and Lewy body dementia subjects, and good post-marketing surveillance are needed to fully understand the utility of this agent.