The signing of the Lateran Pacts between Mussolini and Pius XI not only changed the status of the Vatican, it also transformed its financial position overnight. After decades of financial difficulty, the Vatican acquired a substantial capital endowment, the investment of which the pope entrusted to Bernardino Nogara. But as the diary of Nogara reveals, as a result of the pope's ambitious spending plans, the lack of a proper system of financial control in the Vatican, and, above all, the impact of the Wall Street crash, within less than two years the Vatican was losing money hand over fist. This article explains how Nogara reconstructed the finances of the Vatican in the wake of this disaster, and explores the links between the Vatican's first experience of playing the international capital markets and the pope's notions of social and economic ethics.