The prevailing view among modern critics and translators of the NT is that the adjective μονογενής in John 1.14, 18; 3.16, 18 and 1 John 4.9 means ‘only’ or ‘single’. Against this consensus several authors have recently re-argued the case for interpreting the adjective as ‘only-begotten’, claiming that it does after all include the notion of derivation or birth. By a thorough examination of the use of μονογενής in Greek literature I hope, however, to show that the adjective's usual meaning is in fact ‘unique’ or ‘only’, ‘single’. It will furthermore be argued that this sense best suits the context of the term's occurrences in John as well. Finally, I shall try to show how the interpretation of the Johannine μονογενής as ‘only-begotten’ originates in, and is the result of, developments in Christology which do not antedate the second century AD.