The following Note reports the discovery of an unnoticed manuscript fragment in Adam Smith’s hand, preserved in the Wren Library of Trinity College, Cambridge. The fragment appears to be a draft of a letter of 15 May, 1779 addressed to Louis-Alexandre (1743–92), duc de La Rochefoucauld. The Note reconstructs Smith’s friendship with Rochefoucauld, and considers the significance of the fragment to Smith’s involvement in the publication of David Hume’s Dialogues Concerning Natural Religion (1779). The Note concludes by discussing the anonymous French translation (1779) of Hume’s Dialogues, and the conjectural attribution of the translation to Paul-Henri Thiry (1723–89), baron d’Holbach.