The authors describe a seven months and a half little girl, A.B., affected by multiple localization osteomyelitis caused by an Atypical Mycobacterium, with the culture identifies as M. Avium, belonging to the third group of Runjon classification. The radiographic tests show a primary pulmonary complex and some osteolytic areas of the seventh right rib and of the bones of the lower legs (femur and tibia). From the beginning a multiple antituberculous chemotherapy against non tuberculous mycobacterial disease has initiated: Streptomycin (for two months) associated with Rifampicin, Isoniazid and Pyridoxine. The patient responds very slowly to the treatment and only three years later the whole radiologic regression of the lesions occurs. The interest of the case comes from the extreme rarity of disseminated bone localization during an atypical mycobacterial infection, and also from the early beginning of the clinical and radiologic manifestations.