Early in the twentieth century, Italian Protestants in the United States comprised a religious minority in the Italian Catholic community and an ethnic minority in the American one. Because the assimilation of Protestants from heavily Catholic countries is little studied, I examine the life cycle of three Italian Protestant churches in three denominations in Rochester, New York in order to explain why they disappeared earlier than did their Catholic counterparts. When the second generation Italian Protestants attained adolescence, religious identity with American Protestants overrode ethnic identity, accelerating their assimilation. The Italian Protestant churches had become middle-class American organizations save for the use of Italian, a fatal contradiction. By 1960,all three churches had died, but all of the ethnic Catholic and national Orthodox parishes had survived.