Unfamiliar territory of the international historiography, the spread of the Reformation and its confessional organization in Hungary and Transylvania shows specifics ways, very different from the same process in other European countries. The three parties of Hungary, divided since the second third of the 16th century, experienced radically different religious policies. In addition to these differences of destiny for more than a century and a half, these three parts of Hungary had a great religious diversity. Because of these particular conditions, the history of the diffusion of the Reformation in the Hungarian territories is a particularly rich field of research.