This study investigates the correlates of incidental or nonpurposive health information use on the Internet. Through a secondary analysis of the Health Information National Trends Survey II data, this study reveals that incidental health information use on the Internet is positively associated with overall Internet use, active health information seeking on the Internet, and incidental health information use from traditional media. Thus, this study extends the notion of media complementarity to incidental media usage in a health communication context. This study also reveals that adults who have been diagnosed with cancer are more likely to have incidental health information use from traditional media but not the Internet. More important, this study suggests that incidental health information use on the Internet is positively associated with health knowledge. The findings have important implications for health information campaigns on the Internet.