In this chapter the neuroscientific basis and clinical rationale of cognitive psychopharmacology are reviewed. Effects of drugs in humans and animals are surveyed on different forms of memory and a number of aspects of executive function, including attention, working memory, cognitive flexibility, and response inhibition. The main drug classes covered include the benzodiazepines and the stimulants, but their cognitive effects are mainly analyzed in terms of their neurochemical modes of action, for example, at GABAergic, glutamatergic, monoaminergic, or cholinergic receptors, and in relation to their neuroanatomical sites. Particular attention is paid to cognitive-enhancing drugs and their prospects. The main factors determining the benefits and costs of drugs on cognitive performance are identified. The utility of psychopharmacology in dissecting cognitive processes is also considered.