Research findings concerning a class of rational strategies that emphasize linking schools with outside knowledge and expertise are summarized, with special attention given to findings from five recent or soon-to-be-completed studies. This report consolidates, organizes, and interprets the quantitative research evidence concerning the roles, activities, job contexts, and effects of external linking agents and agencies on school improvement outcomes, and examines the role of the external linking agent in terms of a larger set of internal and external factors that affect these outcomes. Five issues are addressed specifically: (1) recent research findings implications concerning linking agents; (2) linking agent roles in actual practice; (3) evidence concerning the effects and outcomes of linking agents' efforts; (4) implications of recent studies for the selection, training, and support of linking agents; and (5) study implications for the initiation, continuation, or modification of efforts employing linking agents to improve United States schools in the l980's. An eight-page reference list, a four-page bibliography, and an additional publication list for DESSI (A Study of Dissemination Efforts Supporting School Improvement) publications are included. (Author/LMM)