Although the White Sisters were the second most important missionary group in Belgian Rwanda during the interwar period, the scientific literature generally ignores them. Were those Catholic nuns really so retiring in Central Africa? This article reviews the situation regarding their medical activities in interaction with the colonial State and the White Fathers. It points out their contradictions and ambiguities regarding the colonial domination, and their dependency upon the Catholic hierarchy. The health field proves to be propicious to an increasing presence of the White Sisters in the public arena, and to their quest for autonomy.