In the forties of last century, American Protestant missionaries, sent forth by the American Board of Commissioners for Foreign Missions, were working among the Assyrian (Nestorian) Christians in northwestern Iran. Nearly ten years after its beginnings, the 'Nestorian mission' went through a difficult period. Not only had the mission to cope with opposition from Roman Catholic missionaries and the Persian government, but also with internal quarrels about the preferred policy of the mission. The internal conflict concentrated on the employment of Assyrian bishops by the mission. Some of the missionaries were convinced that the earlier cooperation of the bishops with the mission was only to be attributed to the fact that they received salaries, rather than out of conviction. Even more, the mission's employment of the bishops could be understood as its approval of the episcopal organisation and various customs of the Assyrian Church. For some of the missionaries, these consequences were hard to accept. Their opponents within the mission greatly valued the positive aspects of the employment of the bishops: it provided the missionaries with good opportunities to preach among the Assyrians, at the same time showing the Assyrians that the Protestants' main aim was not to subvert their customs but to stimulate a revival within the Assyrian Church. In this article, I have argued that it were these opportunities for preaching among the Assyrians which constituted the main reason for Rufus Anderson to support the latter party, even if some aspects of their policy were not in line with the general policy of the American Board of that time. As to the reasons for the Assyrian bishops to work with the American missionaries, I assume that both 'spiritual' and 'material' aspects were involved; the main reason, however, not being the bishops' attraction to the Protestant faith as such, but to the process of modernization and emancipation which the Protestant mission was thought to represent.