The first part of this article describes the way the portuguese tried to unite and then religiously assimilate the Syrian christians in Kerala.The latter made up of merchant groups that were not integra ted in caste structure but that pretty much reflected its internal characteritstics, especially endogamy.This assimilatory process was aimed first of all, at the reli gious system of beliefs and expression by trying to impose the latin rite. But religious organization was also subjected to change through the imposition of a new religious hierarchy that was to replace the old lineage-based organisation: priests as lineage heads, especially. The diamper synod was one of the key. Factors in this process which ended however in failure and resulted in the breaking up of the Syrian group. The second part of the article deals with the establishment of new Christian groups and the con version of lower castes by the portuguese. One way conclude by saying that the Christians remained outside of the caste system proper outwardly characterized by the belief in Hindu divinities, yet they fall into groups bearing its internal social characteristics.