The use of a medical library by members of the faculty of a medical school was studied by questionnaire. An attempt was made to ascertain the part the library played, among the channels of communication, in work-related information searches. Generalizations of former use studies (suggesting that the choice of formal versus informal source was influenced by experience, type of work, task, and accessibility) were tested on a new population. The study attempted to describe the population of users and the kinds of sources they used in an information search, and to identify some of the factors which influenced their choice of kinds of sources. It was hoped that a study of the factors influencing the use of information sources would lead to the possibility of predicting use of kinds of sources once the characteristics of the users were known. The results refer mainly to the information searching of clinicians affiliated with a teaching hospital. Most frequently sought information was about a specific disease. The study showed high use of informal sources in seeking information. Talking to a man in the same subject area as the respondent was the most common method used. The major source which provided the information was journal articles. More than half of these articles were used in Xerox copy form. The importance of personal collections as sources of information was pointed up. Most respondents found the information they sought themselves, rather than relying upon library services. The use to which the information was put v/as evenly divided between clinical and research, although the majority of the respondents were clinicians. A connection between experience and type of source used appears to exist. The high use of informal sources suggests that type of work may influence method of search. Research appears to lead to more information searches than teaching. The study brought out a high use of sources which are accessible and easy to use. The tabulations show the importance of co-workers in informal communication. Low delegation of documentation tasks to libraries is apparent. The main user of the library studied v/as a clinician in the area of internal medicine who used journal articles about diseases for information to use in the treatment of his patients. Most talked to men in their subject areas to find a source and did not use library services. Telephoning wa3 widely used as a means of contacting the library. The card catalog was little uced by the patron. Of those who went to the library, more than half used indexes or browsed on the shelf. The recommendations were made that journals should be shelved accessibly, with Index Medicus nearby. Books might be shelved less accessibly. Telephone access to the library is of major importance as is the provision of adequate Xeroxing f a c i l i t i e s.