This paper, which updates and expands on the first edition (1981), begins by presenting a definition of instructional development (ID) and a discussion of its origins. A taxonomy for classifying ID models is then suggested, and it is noted that most ID models have been subjected to only a limited degree of testing. The 12 ID models that are reviewed are divided into the three categories specified by the taxonomy as they focus on the classroom, the product, and the systems. Specific models are described and discussed in each of these categories: (1) classroom--Gerlach and Ely; Heinich, Molenda, and Russell; Dick and Reiser; and Kemp; (2) product--Van Patten; Leshin, Pollock, and Reigeluth; and Bergman and Moore; and (3) systems--IDI (Instructional Development Institute); ISPISD (Inservices Procedures for Instructional Systems Development); Dick and Carey; Seels and Glasgow; and Diamond. The taxonomy and 11 of the 12 models are depicted in 12 figures. A guide to searching ERIC for ID models is provided in the Foreword, and the annotated ERIC bibliography lists 19 journal articles and 14 documents. Instructions for obtaining copies of ERIC documents and journal articles are included. (30 references) (DB)