As computers and computer networks become more sophisticated, a huge amount of text-based information, such as that found in web documents, emails, and business related documents, has been accumulated and circulated. Such information gives people a framework for organizing their daily life, and is starting to have a strong influence on governmental policies and business management. Our society needs technology that exploits this wealth of text-based information for a wide range of purposes: extracting credible information related to a given topic (particularly when the query has returned answers from large documents); organizing extracted information in a purpose-oriented manner; classifying information into predefined classes such as facts and opinions, and so on. This e-book is based on papers selected from those presented at the First Workshop on Information Credibility on the Web, which was held in Miyazaki, Japan, on June 19, 2007, in the context of the 21st Annual Conference of the Japanese Society for Artificial Intelligence. The aim of the workshop was to provide a forum to have discussion on broad issues related to the credibility of information on the Web, including not only technical but also social aspects.