Picornaviruses infecting pigs, described for many years as "porcine enteroviruses", have recently been recognised as containing viruses within three distinct genera (Teschovirus, Sapelovirus and Enterovirus). To better characterise the epidemiology and genetic diversity of members of the Enterovirus genus, faecal samples from pigs from four provinces in Vietnam were screened by polymerase chain reaction using conserved enterovirus-specific primers from the 5' untranslated region. High rates of infection were recorded in pigs on all farms, with detection frequencies of approximately 90% in recently weaned pigs but declining to 40% in those aged over one year. No differences in EV detection rates were observed between pigs with and without diarrhoea (74% [n=70] compared with 72% [n=128]). Genetic analysis of consensus VP4/VP2 and VP1 sequences amplified from a subset of EV-infected pigs identified species G EVs in all samples. Among these, VP1 sequence comparisons identified six type 1 and seven type 6 variants while four further VP1 sequences failed to group with any previously identified EV-G types. These have now been formally assigned as EV-G types 8-11 by the Picornavirus Study Group. Comparison of VP1, VP4/VP2, 3Dpol and 5'untranslated regions of study samples and those available on public databases showed frequent, bootstrap supported differences in their phylogenies indicative of extensive within-species recombination between genome regions. In summary, we have identified extremely high frequencies of infection with EV-G in pigs in Vietnam, substantial genetic diversity and recombination within the species and evidence for a much large number of circulating EV-G types than currently described.