Blood samples were taken from 39 black rhinoceros (Diceros bicornis), usually soon after they were captured. The blood was examined microscopically for trypanosomes, and most samples were tested for trypanosome serum antibodies and inoculated into small laboratory animals. Serum antibodies were found in most animals and trypanosomes identified as Trypanosoma brucei were found in 7 of 39 (18%) of the rhinoceros. Berenil (diminazene aceturate) did not effect complete elimination of trypanosomes. In spite of treatment, one rhinoceros died of trypanosomiasis.