The authors described three acute paracoccidioidomycosis patients with bone marrow involvement. P. brasiliensis yeast forms were observed in bone marrow smears of all them, and in one case, culture also revealed fungus growth. The mononuclear phagocytic sistem involvement, the blood eosinophilia and the negative skin hipersensibility responses were emphasized in all of them, as well as the severity of the disease in one case, with disseminated bone lesions and 20.260 eosinophils/mm³ in peripheral blood. The authors discuss the possible role of eosinophil in the host-parasite interaction in paracoccidioidomycosis, suggesting that TH 2 subpopulation activation and increased IL 5 and GM-CSF secretions may be responsible by eosinophilia in the most severe case