A recurring problem for marketing communication planners is the nature of the hierarchy of communication effects. Does awareness lead to comprehension to conviction and then to purchasing behavior? It depends. In fact three kinds of hierarchies are posited in this paper: the standard Learning one mentioned above. the Dissonance-Attribution hierarchy in which action occurs first, then attitude shift and finally awareness and comprehension. the Low-Involvement hierarchy originally developed by Herbert E. Krugman. For low-involvement situations, awareness and minimal comprehension occurs first, then purchasing action and finally attitude or conviction change. By reviewing his own program of research, the author provides guidelines for planners who want to know when these hierarchies are most likely to occur in response to a communication campaign. Briefly, the standard Learning hierarchy seems to occur when buyers are involved, alternative products are clearly differentiated, mass media promotion is important and the product is in the early stages of the product life cycle. The Dissonance-Attribution hierarchy—with purchasing action first— seems to occur when buyers are involved, products are similar, personal i selling is more important, and the product is in the early maturity stage of its life cycle. The Krugman Low-Involvement hierarchy occurs when involvement is low, products are seen as similar, broadcast media are important, and the product is in late maturity. By the way, the Low-Involvement hierarchy is observed most often in the author’s laboratory research program. The laboratory repetition research on which this paper is based was supported by the American Association of Advertising Agencies Educational Foundation. The paper will appear later this year as a chapter in Volume 2 of the Sage Communication Research Annuals. Research Paper Series