BACKGROUND: The goal of this prospective, cross-sectional study was to determine the user demographics of a digital health sciences library (DHSL), motives for use, the nature of users information requests, and success rate in finding answers. METHODS: The content of 500 consecutive electronic mail messages (e-mails) submitted to a DHSL were analyzed using a predetermined coding scheme. Data were entered into a database and frequency analysis was performed. RESULTS: The number of information requests from the 500 e-mail messages was 751. The largest sender category was patients and laypersons followed by students, then physicians. Motivations for use were primarily medical advice (42.8%) and patient care (13.8%). E-mail subject areas were mainly medical (61.8%) and technical (20.6%). Answers to information requests were found 54.3% of the time and senders felt the DHSL was valuable (97.8%). CONCLUSIONS: A DHSL is a valuable medical resource. DHSLs must serve the broad information needs of patients and laypersons in addition to health care providers. Developers and managers of DHSLs can use this information to guide future development of DHSL information content and services, as has been done at The University of Iowa.