With the growing usage of the Internet, the demand for online health care information and advice as well as the number of health-related Web sites are increasing. In case of online health information and advice, the user interface replaces face-to-face communication. To ensure that the users' needs are met, it is critical to balance functionality and usability in the design of the Web site. The present study seeks to identify the complex interrelationships among the various factors of usability and functionality concerning e-health Web sites. Two Turkish e-health Web sites were assessed for evaluation in this study. The findings show that the users of the health information Web sites give a higher priority to functionality and its factors, whereby the highest relative importance is on services/facilities and personalization/categorization of information. The most important usability factors related to the e-health Web sites are memorability and interaction. (c) 2012 Wiley Periodicals, Inc.