This study explores why people participate in health-related Internet activities and what the potential impacts of such activities are. Specifically, this study examines how trust in health information (i.e., from a physician and from the Internet) determines individuals' health-related Internet activities and whether this use subsequently improves outcomes such as discussion with doctors about online health information and satisfaction with health care. Findings from a Web-based survey in South Korea indicated that trust in health information from doctors decreased communication activities, whereas trust in online health information increased both communication and information activities. Both communication and information activities increased discussions with doctors about online health information, which subsequently led to satisfaction with health care.