In antiquity, the term historia was invented by the Greeks. Historical records were written by historians relying on various sources in much the same way that a modern historian would. To the ancients, however, there were largely two sources of historical data. One was the written sources which included documents and information, both epigraphic and numismatic. The other was the unwritten sources embraced by the terms muthos and logos, being the totality of oral testimonies about the past and now regarded as oral traditions. It is the aim of this paper to examine, as far as workable, the development of muthos and logos as oral traditions and attempt a portrayal of their uses in Greek histories. The paper submits that these two terms are veritable catalysts in the development of Greek historiography.