Jews living in the Christian kingdoms of Iberia in the first centuries of the Reconquista encountered favorable conditions but growing social tensions between Jews and Christians erupted in Seville in the summer of 1391, when the kingdom of Castile experienced a period of interregnum. Disorder and riots spread to the rest of Castile, to Andalusia, and to Aragon. Jewish communities were decimated or destroyed, with many of their members killed or forcibly baptized. These events created the social group of converts to Christianity, called New Christians or conversos by Iberian Old Christians, that is, Christians of non-Semitic origin. This volume presents a systematic and detailed elaboration of the halakhic (legal) decisions written by five of the most important authors who wrote responsa concerning conversos between the years 1391 and 1492. The expulsion was an event that radically changed the perspectives of the Iberian conversos. The halakhic authorities were confronted with an absolutely new situation, in which they had to reformulate their position towards the conversos. This volume presents all the responsa written in connection with conversos by Isaac b. Sheshet Perfet, Simeon b. ema Duran and his descendants: Solomon b. Simeon Duran, ema b. Solomon Duran and Simeon b. Solomon Duran.