This report presents findings of the first national survey of U.S. library networks undertaken by the National Center for Education Statistics (NCES) from 1977 through 1979. A definition of library networks as used in the survey is provided, as well as information on the organizational type, general characteristics, nature of participants, expenditures, funds, staff, computerized support, services and activities of library networks. The first section of the report provides a summary or explanatory material for the library network data which is more fully presented in 14 statistical tables comprising the second section. Selected report findings are listed as follows: (1) there were 608 library networks in the United States in 1978 with 32,148 participants; (2) participants included academic, public school, public and special libraries, and state library agencies; (3) 60 percent of library networks were publicly administered and 72 percent were regional in service; (4) 87 percent of network staff were paid, with 23 percent of paid staff being librarians; (5) networks received $193.6 million in 1978; (6) the largest network expense was salaries and wages; (7) networks provided acquisitions, cataloging, reference, circulation and administrative services; and (8) 59 percent of library networks had computer support. An appendix briefly discusses the survey methodology. (ESR)