Abstract: After the 1968 emigration, very few Jews remained in Poland, and even more miniscule was the number of “Jewish Jews.” Since then the number has grown somewhat, and much of it is due to the process of de-assimilation; i.e., some people with Jewish ancestors raised in completely Polonized families began to recover, reclaim, and readapt their Jewish background. An analysis of this phenomenon is offered with a series of putative reasons for its occurrence. The individuals constituting the “products” of de-assimilation are the majority of Polish Jews today and form much of the current leadership. While individuals everywhere can strengthen their ties to the Jewish people and can experience teshuvah or another kind of “Judaization,” the process of de-assimilation does not seem to be reducible to those moves. It begins with no Jewish identity, and is highly dependent on the attitudes and cultural trends in the majority society. It does not remove the de-assimilationists from the majority culture. The phenomenon is general and deserves to be studied as a sociological mechanism working in other cases of assimilation to a majority culture. In the Jewish case, it is especially dramatic. Probably the first example can be found in the evolution of the Marrano communities settled in Holland. The presence of de-assimilation seems to differentiate some European, first of all East European, communities from the globally dominant American and Israeli ones. Probably this rather new concept is needed to describe a significant part of the world of the Jews of twenty-first century Europe.