Thomas Aquinas was introduced to the New Aristotle at the University of Naples and, after becoming a Dominican, studied under Albert the Great at Cologne and edited Albert’s commentary on the ‘Ethics’ of Aristotle. Throughout his career, Thomas exhibits a more-than ordinary interest in the philosophy of Aristotle and an ever deeper appreciation of it. Nonetheless, it was relatively late in his short life that he composed a dozen commentaries on Aristotelian works, spurred on, doubtless, by the controversial use to which Aristotle was put by those in Faculty of Arts at Paris who are variously called Latin Averroists or Heterodox Aristoltelians. These commentaries are among the most careful, helpful, and insightful ever written on the text of Aristotle. It is sometimes mistakenly thought that in them Thomas was somehow baptizing Aristotle, wrenching his thought into conformity with Christian doctrine. No one who reads the commentaries could long entertain this libelous view of them. The translation of Thomas’s Commentary on the ‘Nichomachean Ethics’ made by Father Litzinger has long been out of print. It is here reprinted in a somewhat altered form. The translation itself stands as Litzinger produced it, but the presentation of the Aristotelian text, with accurate indentification of Bekker numbers as well as the mode of referring to Aristotle in the commentary have been changed so that the commentary can function better as a commentary.