Human metapneumovirus (hMPV) is a newly discovered paramyxovirus associated with upper and lower respiratory tract infections most commonly in young children, elderly subjects, and immunocompromised patients. hMPV can cause severe infections such as bronchiolitis and pneumonia and is responsible for 5 to 10% of hospitalizations of children suffering from acute respiratory tract infections. Such infections are indistinguishable from those caused by human respiratory syncytial virus. The first hMPV infection occurs during early childhood but reinfections are common throughout life, especially in older subjects. Molecular methods such as reverse transcriptase polymerase chain reaction (RT-PCR) are the preferred diagnostic modality due to fastidious growth in cell culture. Promising experimental models have been developed to better understand hMPV pathogenesis and to evaluate the potential effect of different therapeutic modalities. No commercial treatments are yet available for hMPV, although ribavirin has shown activity both in vitro and in animal models. Live attenuated vaccines produced by reverse genetics have also shown good efficacy in animals.