Medical writers play an important role in many phases of the clinical drug development process. Measures employed in central nervous system (CNS) studies include diagnostic, efficacy, quality of life (QoL), and safety measures. This chapter provides an overview of some commonly employed measures. The analysis and presentation of efficacy findings is driven by a study's statistical analysis plan. There has been growing attention to the increasing placebo effects noted with some CNS drugs, particularly with regard to antidepressant medications. Any safety concerns that are noted in pre-clinical or prior clinical studies using the investigational product may also be targeted for specific review. Antipsychotic medications have been associated with a number of side effects including lethargy, orthostatic hypotension, extrapyramidal side effects (EPS), tardive dyskinesia, neuroleptic malignant syndrome and QT interval prolongation. Increased efficiency is reflected in the change from paper to electronic submission of regulatory documents.