In the past few years, the term Web 2.0 has become a descriptor for the increased functionality of Web sites, including those with medical content. Most physicians do not know what Web 2.0 means or how it can impact their work lives. This review provides some background on the evolution of Web 2.0 and describes how its features are being incorporated into medical Web sites. Some potential applications of Web 2.0 in pathology and laboratory medicine are discussed, as are the issues that must be considered when adopting this new technology.