Five premises necessary for the formulation of instructional theory are stated. As a suggested elaboration of the "behavior classification" premise, a two-way (content and behavior) classification scheme for higher order tasks is described. The content dimension includes paired associate, concept, principle, and problem tasks. The behavior dimension includes discriminated recall, classification, rule using, and higher rule using. Each two-way category is illustrated by treatments from recent research on higher order tasks. As a suggested elaboration of the "manipulation of task variables" premise, a taxonomy of task variables is described. The taxonomy is divided into qualitative variables and quantitative parameters. The former include the major categories of presentation form, interdisplay relationships, and mathemagenic information (i.e. information designed to promote behavior which gives birth to learning). Parameters include major categories of sequence, quantity, and pace. Research investigating some of the variables in the taxonomy is described and critiqued, and some additional needed research is suggested. A final section indicates implications of this research and the task taxonomy for instructional development. (Author)