This discussion of validation procedures for learning hierarchies based on an analysis of a target skill of instruction to aid in the instructional development process indicates that there is no catalog of validated hierarchies available for this use, and that the literature provides little assistance to the developer seeking practical procedures. A recent study by White and Gagne is discussed in the context of the use of posttesting as a validation procedure for such hierarchies, and the need for further investigation to extend this study is indicated. Practical suggestions based on research and practical experience with learning hierarchies are provided for instructional developers, and 22 references are listed. (LLS)