BACKGROUND: Digital health sciences library (DHSL) evaluation involves studying the usage of the DHSL by individuals as well as populations. The purpose of this study was to evaluate trends in overall usage of a DHSL as part of a process of continuous quality improvement in order to learn how to enhance a DHSL in order to meet its users' needs better. METHODS: Web server log file analysis was performed on a prototype DHSL, the Virtual Hospital, using two log file analysis programs on data from the month of February over four consecutive years, 1995 to 1998. RESULTS: Overall DHSL usage increased between 1995 and 1997 and leveled off in 1998. Fifteen percent of usage came from countries outside the United States. A broad spectrum of medical information for health care providers and patients was accessed and centered around specialty medical information. CONCLUSIONS: To be of optimal assistance to users, DHSLs should (1) contain a broad base of information on common and uncommon medical problems, (2) accommodate the needs of the significant percentage of users that are international through content translation and mirroring, and (3) ensure they are indexed and catalogued in the major Web search engines and Web general and medical indices so they can be easily found by users.