Description: Nineteen non duplicate A.baumannii strains, isolated from different clinical samples and samples, from the environment in ICU at Military Medical Academy /MMA/, Sofia, were investigated. The strains were estimated as phenotipicaly equal according to their biochemical characteristic and the resistance` pattern to antimicrobial drugs. The data, obtained by RAPD PCR with DAF 4 primer show 7 discrete clusters / A- G / of strains formed according to their genotype. Group B includes 9 A.baumannii strains. Two of the strains / NN 2,3 / are isolated from nebulizers of oxygen providing system in ICU, six strains from tracheal secretions also from patients in ICU and one strain / N 11 / from drainage in patient originating from chest surgery. The generated PCR fingerprinting demonstrates that the strains investigated are probably clonal related that means that the nebulisers are possible source of infection and that probably an epidemic strains can spread between the patients in different units in the hospital