Begins with a review of the policies that govern the weeding of collections in the MIT library system, particularly the conservation of space, the need to keep abreast of changing educational programs and the need to reinstate collections as programs return to activity. The preparation of budgets to accomplish these goals and the deselection process are described, followed by a discussion of the actual weeding process in terms of different types of materials, such as monographs, serials, technical reports, government documents and society-sponsored papers.