In this article cognition assessments as outcome measures in CNS drug development research are described. An outline is given of the various choices that can be made and the reasons for them, depending on the approach followed. First, a brief historical context is provided of the psychological sciences that have contributed to today's psychopharmacology of cognition assessment. Subsequently, the focus is on identifying cognitive domains and criteria for selecting appropriate tests. In applied cognitive performance assessment in human psychopharmacology, a number of approaches can be recognised, each associated with models that connect cognitive functions with physiological functions and neural structures. The product-oriented approach of cognition assessment is usually characterised by the use of a battery of several cognitive tasks as an assessment instrument and aims to demonstrate an effect of a pharmaceutical substance without much attempt to determine which cognitive process is primarily influenced by a drug. The process-oriented approach precisely defines the cognitive process in terms of at least a single factor linear model of a process (e.g. by manipulating levels of difficulty) and then compares how diseases and drugs modify the parameters of that process. The associated factor analytical, resource-strategy-and staged information processing models respectively are described. Finally a brief review is presented on possible physiological markers or biomarkers of human cognitive functions.