This essay explores some of the interpretive problems posed by the missionary work of the American Board of Commissioners for Foreign Missions among Minnesota's Dakota Indians in the mid-nineteenth century. Since “success” in conversion has often been defined largely in terms of Native American assimilation to white American societal norms, I argue that the Dakotas' acceptance of a Christianity that was preached to them in their own language poses a problem for understanding what “conversion” meant in this case. The difficulty of knowing what Christianity meant to the Dakotas, a difficulty I see as rooted in the problems attendant upon translation, can be illustrated by showing how distorted some of the missionaries' translations of Dakota religious ideas into English were. Their translation errors took two forms: the postulation of a similarity in reference between Dakota and English terms where it did not exist (as with the English words “god” and “spirit” and what the missionaries identified as their Dakota counterparts), or, conversely, the heightening of differences between Dakota and Protestant Christian religiosity (an effect achieved by associating Dakota terms with English pejoratives). I argue that what unites these two differing types of distortive translations is the missionaries' failure to understand the conceptual universe, or “deep structure”, underlying the Dakota language. And since they failed to perceive the holistic character of this conceptual system, the missionaries may have concluded that they had effected conversions among the Dakotas when they had only scratched the surface of Dakota religiosity.