The concept of an algorithm derives from the physical sciences, but it has often been misunderstood and misapplied in the social sciences and in education. The theoretical and practical significance of algorithms stems from their applicability to problems of learning, instruction, and instructional design, and they may potentially provide the basis for the development of a paradigm or model of instruction. For the purposes of this paper, an algorithm may be defined as a strictly replicable procedure which always produces the correct result when applied by a user to a problem or class of problems. Examples of the specification and use of an algorithm are provided together with a discussion of the properties and characteristics of algorithms. Some areas for further investigation and clarification are also suggested. (DGC)