Apart from sourcing formal knowledge ratified and stored in corporate sources such as organizational best practices etc., the Internet and advanced information/collaborative technologies also allow knowledge workers to tap informal knowledge from networks such as discussion boards, SIG-based Wikis, communities of practice, Email/Listserv, etc.. However, some knowledge may reside implicitly within the organization and may not be available in organizational repositories, or in formal knowledge repositories outside of the organizational boundaries (e.g. published case descriptions). In such situations, the knowledge worker may need to use discretion in deciding whether to use formal or informal knowledge source, particularly when faced with equivocal knowledge from the two sources. We formulate testable theoretical propositions to explain the influence of cultural traits of the knowledge worker such as Individualism-Collectivism, Power Distance and Uncertainty Avoidance on choice of the source in such situations. An experiment is designed to investigate how knowledge source would affect perceptions about knowledge usability to knowledge workers from different national cultures. This study would provide knowledge management researchers and practitioners with insights on how culture affects the value of knowledge from different sources through the use of Internet-based technologies.