Parechoviruses are a recently established group of human viral pathogens. At the time of their first isolation, parechoviruses were classified among the enterovirus genus in the picornavirus family, but based on their different biological properties they were separated into their own genus. The type member is human parechovirus 1 (HPEV1), which frequently infects humans, in particular small children. The parechovirus genus also includes HPEV2 and the Ljungan virus, which was recently isolated from rodents, is a candidate for the group. Seroepidemiological studies have shown that the prevalence of HPEV1 antibodies is surprisingly high, exceeding 95% in adult populations. According to present data, HPEV1 causes mainly gastrointestinal and respiratory infections; however, severe disease conditions, such as myocarditis and encephalitis, have also been reported. HPEV2 infections appear to be rare, and it is currently not known whether the Ljungan virus can infect humans.