The human meta pneumovirus(hMPV) is a recently identified Paramyxovi rus associated with acute respiratory tract infect ions(ARIs) ranging from upper ARIs to severe bronchiolitis and pneumonia in humans. We studied the prevalence of this new virus in Seoul from 2005 to 2006 A total of 757 specimens were collected by nasopharyngeal swab from ARI patients and were tested fo1' the presence of hMPV by reverse transcription-PCR. Of these‘ 28 were detected the L gene of hMPV. The age range of the patients with hMPV infection was 1 months to 67 years with similar numbers of females (59 .3%) and males(40.7%) . The main symptoms were cough(100%) , fever (82 .1%) , nasal mucus(67.8%) ‘ vomit(25%) . diarrhoea( 21. 4%). and difficult breathing(21. 4%) and the main diagnosis we1'e pneumonia, bronchioli tis, nasoharyngiti ts, and rhmJtls Virus activity peaked in March and May. Phylogenetic analysis of the N gene confirmed the existence and si multaneous circulation within one epidemic season of hMPV isolates belonging to two genetic lineages.