This article presents three of Arnaldo Momigliano's letters in the author's possession. All concern Momigliano's responses to criticism, and taken together they show his openness to criticism candidly offered within the context of friendly relations. They also reveal his impatience with indirect, insensitive, or ill informed criticism, as well as certain problems that arose from incomprehension (as in the case of Ronald Syme). The first letter was addressed to the author, the second to Professor Christopher Jones (now at Harvard, formerly at Toronto), and the third to Professor Sir Fergus Millar (Oxford). Jones entrusted the second letter for publication, and a copy of the third was given to the author by Momigliano himself.