The Thesis explores the Venetian Inquisition's handling of cases involving crypto-Jewish, crypto-Muslim practices and some cases where people had lapsed into Islamic ways, especially when in remoter parts of the Venetian empire or within the Ottoman empire and who sought reconciliation with the Catholic Church. Despite their differences, the offences involved the practice of dissimulation and connected with Venice's position as a transit city, since for most offenders, Venice was one among their various destinations in their peregrinations in the Mediterranean. The Thesis draws on the printed transcripts of cases involving Judaism, but also unpublished archival material in both the State archive, and the Patriarchal archive. The discussion, with close textual analysis focuses on the lengthy testimonies given before the Inquisition by a variety of people, who appeared as accusers and witnesses, and examines what they perceived as alleged crypto-Jewish and crypto-Muslim practices in the atmosphere of growing concern about religious deviance in late Renaissance Venice. It analyses the tribunal's approach to the accusations and offences, and changing patterns of practice, paying close attention to the Inquisitors' questioning strategies. As most offenders had undergone conversion, this Thesis analyses how they fashioned their identity in front of the Inquisitors who, on the basis of Church and State regulations, insisted on unambiguous religious identities. The Thesis delineates the convergences and divergences in the handling of these offences, and challenges some perceptions of power relations between accusers and accused. While following these investigations, much is revealed about communities in cosmopolitan Venice, their locations and inter-actions, and how Christian and non-Christians perceived, and mis-perceived, each other. Insights are also provided into movements of individuals - as for commercial or mercenary military purposes - in and between remoter parts of the Venetian empire and the Ottoman empire.