This article deals with the Belgian colonial authorities’ obsession with classification and categorization, and explores how this obsession affected medical care in the city of Coquilhatville. Whereas the authorities aspired to medical care that was strictly segregated along ‘racial’ lines, providing separate hospitals for Europeans and Africans, in reality such rigorous segregation was unsustainable. I argue that it was the authorities’ inclination to categorize patients that eventually blurred the lines. Indeed, this article shows how the administrators became thoroughly enmeshed in their taxonomic zeal when members of the African upper class, the so-called évolués, demanded different treatment from other Congolese, to reflect their status. Furthermore, these upper-class patients insisted on being differentiated among themselves too. Responding to more and more claims to be discerned from yet another ‘lower’ évolué, and in an attempt to translate social space into physical space and thus provide the applicant with a more sophisticated hospital room, the authorities gradually ran out of options. As a consequence, they – albeit unwillingly – opened the doors to évolués of a hospital that was initially reserved exclusively for Europeans.