Positron Emission Tomography (PET) studies have demonstrated that a therapeutic window of dopamine D2/3 receptor occupancy (60-80%) is associated with clinical response in younger patients with schizophrenia. This observation has been used to predict the therapeutic dose range and contributed to current recommended antipsychotic doses. To date, there is no published report to examine D2/3 receptor occupancy associated with clinical response in older individuals with primary psychotic disorders. This has has impeded the implementation of treatment guidelines.