Recognizing that the Church cannot be encompassed by a single and eternal ecclesiology, and that there are stages in the development of the Church's self-understanding, the author examines the history and development of two of the dominant twentieth century models : the earlier Mystical Body ecclesiologies, and the post-conciliar Communion/ Koinonia models. They contain interesting parallels, one of which is the risk of ignoring the concrete Church — the mystery manifested in history. What ecclesiological models may next rise to dominance?