Consumer opinion Web sites enable consumers to post reviews of products and services or view the experiences of other consumers. This form of writing can be considered a truly digital genre, as consumers were not able to share their opinions with other consumers in a structured, written format before the advent of the Internet. To identify rules and conventions established by the genre community, a sample of 358 product reviews was examined using a methodology that combines elements of case study research, corpus linguistics, and textual analysis. More precisely, the analysis focused on structure, content, audience appeals, sentence style, and word choice. The results of this analysis have implications for improving the design of consumer opinion Web sites with a view to making them more useful sources of consumer knowledge.