In the last years the number of Bartonella species significantly raised, often with an epidemiological profile of emergent disease. B. bacilliformis is the etiological agent of Carrion's disease. B. clarridgeiae has been associated, together with B. henselae, to Cat-Scratch Disease (CSD), whereas B. elizabethae to endocarditis and B. grahamii to neuroretinitis. B. henselae has been associated to CSD and, in patients with immunodeficiency, together with B. quintana, to bacillary angiomatosis, to peliosis and to endocarditis. B. quintana is the etiological agent of "trench fever", in its "classical" and "urban" form. B. vinsonii subsp. arupensis and subsp. berkhoffii have been associated to bacteremia and endocarditis. The diagnosis foresees pathological examination of the lesions, germ isolation and use of specific serological test and of polymerase chain reaction. Prognosis is, generally, favourable. Therapy foresees the use of numerous antibacterial agents, like: penicillins, cephalosporins, aminoglycosides, tetracyclines, macrolides, quinolones, trimethoprim-sulfomethoxazole and rifampicin.