Effect of Trypanosoma congolence and T. brucei mixed infection on ability of the bone marrow to respond to anemia was investigated in albino rats. This was with the view of assessing the possible impact on recovery rate from anemia following chemotherapy of African trypanosomosis. The investigation involved descriptive evaluation of packed cell volume and corresponding bone marrow cytological changes associated with single and mixed infection of T. congolense and T. brucei. It involved laboratory based experimental infection of albino rats as research models. A total of 32 adult albino rats of mixed sexes were used for this investigation. The rats were randomly grouped into three groups, A, B, C made up of 8 rats each, and infected with T. congolense, T brucei and mixed infection of these species.. Eight other rats served as the uninfected control group.Parameters measured included weekly packed cell volume (PCV) and differential bone marrow cytology of the different groups of infected and control rats at the end of 21 days post infection (PI). At the end of 21 days PI, the anemia characterized by drop in PCV was most severe in the mixed infection group, and least in T. brucei group with tendency for self-recovery from anemia. The bone marrow responses in the mixed infection group was however weak and inferior to that of T. brucei and T. Congolense groups. Poor erythropoietic response in the mixed infection group despite significant fall (P < 0.05) in PCV level was believed to arise from severe renal and hepatic pathology resulting to subnormal erythropoietin release and severe stem cell injury. This is believed would cause longer time to be taken by mixed infection animals to recover from anemia after chemotherapy. It is concluded that T. congolense and T. brucei mixed infection result to marked incapacitation of the bone marrow and ability for recovery from anemia. This suggests that supportive administration of synthetic erythropoietin may be required in trypanosome specie mixed infection situation due to severe pathological effects on the kidney and liver resulting to impaired erythropoietinbiosynthesis and slow recovery from anemia following chemotherapy in African trypanosomiasis.Keywords: Anemia, bone marrow, mixed infection, rats, trypanosomiasis, erythropoietin. DES REPONSES COMPARATIVES DE LA MOELLE OSSESUSE DE RATS ALBINOS INFECTES EXPERIMENTALEMENT AVEC DES ESPECES UNIQUES ET MIXTES DE