Cystic echinococcosis (CE)--caused by the larval stage (hydatid cyst) of the cestode Echinococcus granulosus--is one of the most widespread zoonoses of veterinary and medical importance. Molecular techniques have allowed the identification of 10 different genotypes (G1-G10) of the parasite. The present paper is an update regarding the E. granulosus genotypes infecting water buffaloes and cattle bred in the Campania region of southern Italy. The molecular study was performed on 30 hydatid cysts (11 from water buffaloes and 19 from cattle). Two different mitochondrial DNA genes, namely the cytochrome c oxidase subunits 1 and the 12S ribosomal DNA (12S rDNA) were used as genetic markers. Three different genotypes of E. granulosus were unequivocally identified, i.e. the G1 (common sheep), G2 (Tasmanian sheep) and G3 (buffalo) genotypes, as well as some G1 and G2 variants. It should be noted that the present study demonstrated for the first time: (i) the presence of the G2 genotype in water buffaloes from a Mediterranean area; and (ii) the fact that the analysed portion of the 12S rDNA gene can not discriminate between the G2 and G3 genotypes of E. granulosus. The finding of the G1, G2 and G3 genotypes in large ruminants from southern Italy is of epidemiological relevance and immediate public health importance because of their recognized infectivity in humans.