The purpose of this report was to formulate a definition of health science libraries which would allow them to be objects of study. Four general definitions of health science libraries are presented from the viewpoints of: (1) librarians and managers of libraries as institutions, (2) the institutions or administrative units supporting library operations and service, (3) users of library services, and (4) a suprainstitutional organization or concept, the library network or system. The hypothesis proposed is that a health science library can be identified as an object of study only through the institutional setting in which it operates. (CC)