A study of ninety-five health sciences libraries, obtaining nearly 24,000 user responses, provides estimates of the national cost of library services through the three principal services of circulation, reference, and in-house use; and for four types of users: persons interested in patient care, those interested in research, those involved in education, and others. Unit costs of the three principal services are reported and differences in their relative importance are described. National totals for nine classes of libraries are reported as well as costs by service, user, and function: patient care, research, education, or other. The national expenditure in 1982 was approximately $365 million. The study establishes a method for obtaining results that can be compared and combined across libraries.