Lesions in the spleen and livers of Leishmania infantum -infected BALB/C were studied for 36 weeks and the frequency of mast cells and eosinophils in the lesions were calculated. The tissues were stained with a newly developed method designed to detect mast cells and eosinophils simultaneously. Lesions appeared from week 13 post-infection and both the number and size of the lesions increased gradually and continued as the infection matured. Eosinophils comprised (95%) of the cell types in the lesions and probably play an important role in Leishmania infantum control. In comparison to eosinophils less number of the mast cells was observed in the lesions all the times during the infection
