The aim of the present study was to determine the extent of genome evolution among methicillin-resistant Staghylococcus aureus (MRSA) strains. Three different collections of strains were analysed, comprising locally, nationally and internationally disseminated genotypes. Various genotyping assays displaying different levels of resolution were used. Geographically and temporally diverse MRSA strains comprised the international group. MRSA strains recovered during an outbreak in a New York City hospital and Portuguese MRSA isolates, all resembling the so-called Iberian clone, were included in the local and national collections, respectively. Genotypes were determined by genome scanning typing techniques and procedures which analyse specific DNA elements only. The outbreak strains showed subclonal variation, whereas the Portuguese isolates displayed an increased number of genotypes. Among the epidemiologically unrelated MRSA strains, the different genotyping techniques revealed a wide heterogeneity of types. Different typing techniques appeared to show different levels of resolution, which could be correlated with the extent of geographic spread; the more pronounced the spread, the higher the degree of genome evolution. Binary typing and randomly amplified polymorphic DNA analysis are the typing methods of choice for determining (non)identity among strains that have a recent common ancestor and have undergone yet limited dissemination.Pour evaluer l'evolution genomique des souches de Staphylococcus aureus methicillinoresistantes (SAMRs), trois collections de souches ont ete analysees, comprenant des genotypes disperses aux niveaux local, national et international. Des SAMRs d'origines geographiques differentes se retrouvent dans le groupe international. Des souches recoltees lors d'une epidemie dans un hopital de New York et des souches portugaises, ressemblant toutes au clone dit iberique, ont ete incluses respectivement dans la collection locale et dans la nationale. Les genotypes on ete determines par des techniques analysant exclusivement les elements ADN specifiques. Les souches d'origine epidemique montrent des variations subclonales alors que les portugaises presentent un nombre eleve de genotypes. Parmi les souches sans relation epidemiologique, on observe une grande heterogeneite des genotypes. Les differents niveaux de resolution observes peuvent etre en relation avec la dispersion geographique: plus la dispersion est importante, plus est eleve le degre de l'evolution genomique. Le typage binaire et l'analyse RAPD sont les methodes de choix pour affirmer l'identite des souches ayant un ancetre commun et avant subi une dissemination limitee.