HCoV-NL63, the fourth human coronavirus, has been isolated recently from children with respiratory tract infections, including upper respiratory infection, bronchiolitis, and pneumonia. The virus has been also detected in immunocompromised adults with respiratory tract infections. A total of 118 nasopharyngeal swab samples from 118 hospitalized young children aged less than 2 years with bronchiolitis who were not infected with human respiratory syncytial virus, influenza A or B, or human metaneumovirus were selected. Three (2.5%) of the 118 samples were positive for HCoV-NL63 by reverse transcription-polymerase chain reaction tests. HCoV-NL63 may be one of the causative agents of bronchiolitis in young children. J. Med. Virol. 75:463–465, 2005. © 2005 Wiley-Liss, Inc.