Publically available health Web sites may be able to provide support for teens with chronic disease in their transition to autonomy. This study examines teen use of health Web sites and identifies barriers and promoters of use. One hundred eighty (n=180) teens, aged 13-18, were recruited from asthma and diabetes specialty clinics and given a resource sheet listing selected publically available Web sites. Web sites were categorized as general health, teen health, disease specific (asthma or diabetes), and disease management. One hundred twenty-nine (n=129) participants completed a 3-month follow-up semistructured telephone interview that assessed subsequent use of resource sheet Web sites and collected verbatim comments regarding use. Sixty percent visited at least one Web site from the resource sheet. General health (38.8%) and teen health Web sites (38.0%) were most likely to be visited. Reasons for not visiting any site were categorized as lack of time, lack of interest, lack of Internet access, and lack of medical need. Teen health sites had the highest intention for continued use. Comments associated with willingness to continue use were categorized into the following themes: usefulness, ease, medical need, teen-specific features, and frequency of updates. Neither health literacy nor demographic factors were significantly associated with use. Making a first Web site visit generally leads to a desire for continued use, but teens will not make the first effort of visiting a Web site unless they are engaged and interested in their own health management. Teens are most willing to become regular users of Web sites that they perceive to be useful and to be targeted toward them.