The outbreak of severe acute respiratory syndrome (SARS) in 2003 marked the explosion of health information seeking online in China and the increasing emergence of Chinese health websites. There are both benefits and potential hazards of people's online health information seeking. This article intended to test part of Wilson's second model of information behavior, including source characteristics and activating mechanisms, and to identify the relationships among perceived access, perceived expertise credibility, reward assessment, Internet self-efficacy, and online health information-seeking behavior. Data were drawn from face-to-face surveys and an online survey of health information seekers (N = 393) in China. The results showed that source characteristics predicted activating mechanisms, which in turn predicted online health information-seeking behavior. Activating mechanisms, that is, reward assessment and Internet self-efficacy, mediated the relationship between source characteristics (i.e., access and credibility) and online health information-seeking behavior. Strategies for improving information access, expertise credibility, and Internet self-efficacy are discussed in order to maximize the benefits of online health information seeking and to minimize the potential harm.