Customer reviews play an important role in today's online shopping environment. Research into customer reviews has largely focused on the predictive effect of review characteristics on variables such as product sales. However, relatively little attention has been directed towards understanding how reviews impact a customer's decision to purchase a product. In particular, the mechanism by which reviews influence customers is not well understood. Some studies have suggested that reviews influence a customer's trust in the product and or vendor. However, we propose that reviews impact a customer's perceived risk, in turn reducing their perceived uncertainty. This reduced uncertainty should result in an improved customer attitude towards the product or service, leading to higher purchase intention. As such, we performed three related studies, aiming to improve our understanding of the role of online reviews on customers' risk perception. Particularly, the first two studies (Essay 1: "The Impact of Product Reviews on Purchase Intention: A Study based on the Theory of Reasoned Action" and Essay 2: "How Product Reviews Help Mitigate the Uncertainty in Online Transactions: An Exploration into the Antecedents of Risk Perceptions") explore in greater detail the impact of product reviews first on intention to purchase the product, and then on perceived uncertainty in transactions. In contrast, Essay 3: "Reading the Voice in Seller Reviews: An Analysis on the Trust Felling Revealed by Reviews" examines the impacts of seller reviews on both perceived risk and perceived uncertainty. In general, most of the findings are consistent with our hypotheses. For example, both product reviews and seller reviews have significant impacts on lessening the risks and uncertainty. However, there are also some interesting findings which are slightly different from our initial hypotheses and suggest the path for future studies. For instance, both Essay 1 and 2 reveal that review valence outweighs review quantity in the context of risk reduction, and Essay 3 reveals that, compared to hidden information, customers are more worried about sellers' hidden actions, and additionally the reviews on sellers' integrity and competence are more important than their benevolence. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]