The purpose of this study was to develop and evaluate a method to provide facts about the clientele and use of one type of health science library, the hospital medical library. The method was tested in two hospital libraries, Harper Hospital, Detroit, and Hurley Hospital, Flint. The study was divided into four levels of data collecting and evaluation: (1) a census of all library patrons by category, (2) a division of the libraries into functional units based on areas of service, (3) a survey of use of library facilities which involved the observation of library users, and (4) a summation and evaluation of the data from the census and patron use surveys. It was concluded that this study demonstrates that the functions of the hospital medical library can be an object of study; and this method yields information about a hospital library in varying degrees of detail depending on which steps are carried out and the depth of the data analysis. It was also found that while the steps should be carried out in sequence, useful data are produced when only the first or second step is completed. (Author/JB)