The paper draws together a wide variety of research which relates to the topic of intrinsic motivation; intrinsically motivated activities are defined as those which a person does for no apparent reward except the activity itself or the feelings which result from the activity. Most of this research was not originally reported within the framework for intrinsic motivation, but the paper reinterprets the work within that framework. Several approaches which may account for intrinsically motivated behavior are considered: (1) drive naming; (2) optimal incongruity and optimal arousal; (3) reduction of uncertainty; and (4) competence and self-determination. The paper discusses, compares, and to some extent integrates these four approaches. The report is a first step in bringing together the laboratory work in the basics of intrinsic motivation with the industrial efforts to design jobs so that they contain potential for greater intrinsic motivation for the job holder. Extensive references are included. (Author/SES)