Ever since Giorgio Valla printed his edition and commentary of the Satires of Juvenal, for nearly five hundred years now, scholars have realized the importance of large portions of the commentary. Before putting together his notes and publishing them in 1486, Valla combined them with the material he had gleaned from a mutilated MS, which he for some reason believed the work of Probus. After Valla, nobody ever saw his ‘Probus,’ and it is to be assumed that, having taken what he wanted from the MS, Valla saw no objection to destroying it. A hundred years later, Pithou's discovery of his excellent MS, containing both a superior text of the Satires and a full set of scholia, confirmed the value of Valla's ‘Probus,’ but also revealed the fragmentary manner of its preservation, whether because of its condition when found or because of Valla's omissions. Still another witness on behalf of theses good scholia, also full, appeared at St. Gall and was published by Cramer (Hamburg 1823). During the next century, much work was done to establish an edition of the older and more reliable scholia, first of all by study of Pithou's MS (known as P and so referred to hereafter), the MS of St. Gall (S in most editions and so referred to hereafter), and of ’Probus’ (to which I shall hereafter refer without quotation marks) as elicited from the comments of Valla; then by research into the later, contaminated ‘secondary scholia.’ In the excellent edition by Paul Wessner, the labors of many scholars bore fruit.