Background Human metapneumovirus (hMPV) has recently been recognized as a notable respiratory pathogen in children.However,no isolation processes and only a limited understanding of hMPV epidemiology present in Chinese children are documented by far.Methods Nasopharyngeal aspirates from 86 hospitalized children with acute respiratory tract infections from December 2004 to July 2005 were inoculated onto Vero-E6 cells for hMPV isolation.Total RNA was extracted from infected cells with a cytopathic effect and then subjected to a RT-PCR amplification of the N and F genes of the hMPV.Nucleotide sequences of amplified F gene products were examined using a variation analysis with the MegAlign program and the phylogenetic tree construction using the neighbor-joining algorithm with a Phylip package.Results Six strains of hMPV were isolated from the samples during winter,spring and summer.The most common symptoms were coughing and cyanosis,and the diagnoses were bronchiolitis,bronchopneumonia,infantile asthma,or upper respiratory tract infection.All isolates were in the A2 genetic sublineage and shared a high percentage of homology with the F gene in the nucieotide (99.8%-100%) and amino acid (99.3%-100%) sequences.Conclusions This report indicates that hMPV is an important viral agent for acute respiratory tract infections present in Chongqing,China.Knowledge of phylogeny and genes will benefit the studies on the treatment and prophylaxis of hMPV infection.