Group A rotaviruses are the most frequently detected viral agents associated with diarrhea in infants and children worldwide. It has been estimated that every year almost 120,000 cases of diarrhea associated with rotavirus occur in children under 5 years old in Argentina. In this work, we present the rotavirus strain diversity detected during the first 2 years of the National Surveillance Network for Diarrheas implemented by the Ministry of Health in Argentina. During 2006 and 2007 a total of 464 rotavirus positive samples were G and P genotyped. The predominant genotype combination was G9P[8] (54.1%), followed by G2P[4] (26.5%) and G4P[8] (4.3%). Of note is that four samples were found possessing the G3 genotype, and two the genotype combination G4P[6]. The phylogenetic analysis of the VP7 gene grouped the Argentinean G9 and G3 strains within the lineages currently circulating in humans worldwide, i.e. lineages III and Ia respectively; however, the sequence and phylogenetic analyses of the VP7, NSP4 and the VP8* fragment from the Argentinean G4P[6] strains suggest a porcine origin. In agreement with this, the phylogenetic tree of the VP7 gene from G4 strains suggests the presence of at least two porcine lineages currently circulating in the Americas. In addition, the inclusion of new sequences available in public databases and the sequences reported in this work allowed us to describe new lineages and sublineages within the G4 and P[6] genotypes.