This chapter examines the role that instructional development (ID) can, does, and should play in the public school library program, particularly the ID activities that can be undertaken by the school library media specialist (LMS). The LMS literature is examined to determine the extent to which ID activities are considered, and a factor analysis study is performed to identify the ID activities undertaken by media specialists. An ID diffusion model is presented that is designed to increase the ID activities appropriate for the LMS to perform, and those activities that are not considered appropriate for the LMS to perform are indicated. Recommendations are made for changing the LMS training program, increasing the ID training received by LMS students, and facilitating ID interaction between teachers and media specialists. The text is supplemented by four figures and three tables. (36 references) (Author/EW)