Aristotle's Eudemian Ethics was until recently treated as a poor cousin of the better-known Nicomachean Ethics - poor enough even to have to borrow its three central books (IV-VI) from the latter. The work has now emerged from its relative obscurity; many scholars, indeed, now claim - on the basis of what appear to be sound statistical arguments - that it is the Nicomachean Ethics that has to borrow its Books V-VII from the Eudemian. This critical edition of Aristotle's Eudemian Ethics treats this particular issue as unresolved, including as it does only five books (I-III, VII-VIII), but without prejudice, the three disputed books being treated as already available in the edition of the Nicomachean Ethics in the same series.The new edition of the Eudemian Ethics completes the task, begun by Walzer and Mingay's 1991 Oxford Classical Text edition, of restoring the corrupted text on the basis of a new understanding of the relationships between the extant Greek manuscripts. The three primary manuscripts identified by Harlfinger, along with a fourth identified by the present editor, Christopher Rowe, have been freshly and fully collated, a more extensive apparatus criticus has been provided, and substantial new progress has been made in the restoration of the text. A separate companion volume (Aristotelica: Studies on the text of Aristotle's Eudemian Ethics) contains the arguments for every important editorial choice made in the restoration of the text.