In late 1995, several months prior to the introduction of Internet Grateful Med, the National Library of Medicine (NLM) conducted a customer survey as part of its efforts to make a transition from Grateful Med to new forms of electronic information access and retrieval. A questionnaire survey was mailed to a sample of 2,500 online users randomly selected from domestic users (excluding fixed-fee users) who searched NLM databases during the second quarter of 1995. The final response rate was nearly 83% of eligible respondents. About 70% of NLM customers responding already had access to the Internet, and of those, more than 90% had access to the World Wide Web. However, only 26% of customers with Internet access were using the Internet to access NLM databases. Health care providers account for about 46% of NLM customers but, as a group, search NLM databases relatively infrequently even though they have higher-end equipment. Librarians and information professionals represent about one-fifth of NLM customers and are by far the most intensive users, but tend to have lower-end equipment. Overall, the survey results provide a strong basis for the transition to Internet-based delivery of NLM online database services, including Internet Grateful Med and the NLM family of World Wide Web sites. However, Internet access is uneven, especially in rural areas and at hospitals. This reinforces the need for continuing special outreach efforts directed at improving access for rural and hospital-based users and rural libraries, upgrading computer equipment for medical librarians, and training health care providers in more effective use of Internet-based biomedical information resources.