The Layers of Necessity Model developed by M. Tessmer and J. F. Wedman (1990 and following) proposes that designers create multiple layers of instructional design (ID) activities depending on the particularities of different design situations. To enrich the understanding of the model, a replication was conducted of a study conducted in 1992. Subjects were 66 members of the National Society for Performance and Instruction (NSPI) (Canada). The questionnaire asked how often subjects performed particular activities in ID in a variety of contexts. Questions about the individual's introduction to ID and the references the subject found most useful were added. Responses indicate that there is a consensus among practitioners that the 11 listed tasks form the core of the ID process. While some respondents added tasks, others deleted some to emphasize different aspects of ID. Although there was great heterogeneity of introduction to ID, responses were surprisingly homogeneous. Differences between these responses and those of the previous study are analyzed. One table presents survey findings. (Contains 6 references.) (SLD)