Wildlife mortality involving bongos, Tragelaphus eurycerus, and other ungulates was investigated in the north of the Congo Republic in 1997. Four bongos, one forest buffalo, Syncerus caffer nanus, and one domestic sheep were examined and sampled. Although an outbreak of rinderpest had been suspected, it was found that the animals, which had been weakened by an Elaeophora sagitta infection and possibly also by adverse climatic conditions, had been exsanguinated and driven to exhaustion by an unusual plague of Stomoxys omega.