Information search is an integral part of the consumer decision making process. There is no doubt that the Internet contributes to, and will continue to affect, this function. However, a comprehensive understanding of what causes, motivates, and mediates information search behavior on the Internet is relatively lacking. Based on an in-depth review and critical critique of past research on information search behavior and, in particular, online information search, this chapter offers a causal model of online information search with 16 specific research propositions outlined. It argues that information search on the Internet should be investigated by considering Internet specific factors (i.e., skills, prior online purchase experience, attitude toward the Internet) as well as various antecedents including situational, product-related, and individual factors. Contribution and implications of the model for further understanding of information search behavior in the context of the Internet are also discussed.