Wittgenstein's 'Prototractatus' raises difficult textual questions concerning both its structure and the date of its composition. I provide an account of the structure of the 'Prototractatus' by investigating the hitherto unexplored connections between it and other early Wittgenstein manuscripts. I then consider the two most influential proposals on its date of composition, made by von Wright and McGuinness, and argue that neither of them stands up to scrutiny. I make an alternative suggestion, and discuss its implications for the significance of (...) the 'Prototractatus' in the study of Wittgenstein's early philosophy. -/- . (shrink)