Human metapneumovirus (hMPV) is a pathogenic respiratory virus, discovered in 2001. The virus is part of the family paramyxoviridae and is comparatively closely related to respiratory syncytial virus (RSV). The clinical manifestations of a hMPV infection are rather similar to infections caused by RSV, ranging from mild upper airway disease to severe pneumonia. Detection of hMPV RNA by polymerase chain reaction (PCR) is the only established routine diagnostic method. The virus is easily cultivated in several types of cell culture lines, however, cell pathology (cytopathic effect) is irregularly observed. Our department has developed an indirect immunofluorescence test based on polyvalent rabbit antibodies. This method appears to give reliable results, detecting hMPV both in cell culture and directly on patient samples. Nasopharyngeal aspirate is the preferred material for diagnostic purposes in small children. A nasopharyngeal swab, or alternatively a throat swab, can be used for older children and adults. Samples from lower airways are appropriate under special circumstances. Serology is not available for routine diagnostic use.