This chapter describes the cognitive findings from the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) project, including analyses of the baseline cognitive assessments in 1,331 patients, one of the largest schizophrenia cohorts to be studied with neuropsychological measures, and the effects of treatment on these measures in over 800 patients randomized to five different antipsychotic treatments. The choice of tests for a neurocognitive battery is often controversial. Since the CATIE project promised to yield a rich database, it is important that the batteries of tests chosen for the project receive consensus approval from the leaders in schizophrenia and dementia research. The aim of the CATIE Neurocognitive Assessment Unit training program is for testers and investigators to achieve thorough understanding of the rationale and methods of the neurocognitive assessment protocol, and considerable preparation preceded the production of manuals and training materials.