Abstract
It is the aim of this review to discuss the literature on the effects of some abnormal conditions on human performance. The abnormal conditions are either environmental- e.g. heat, loud noise- or originate from the organism itself- e.g. intake of drugs, sleep loss. Prior to the review, the problems relating to classifications of tasks and drugs are discussed. A tentative pharmacological classification is described with the emphasis on medicines or substances, which are provided or taken while normal work can be continued.