A method is described for the detection of human coronavirus 229E (HCV 229E) in nasal washings using RNA:RNA filter hybridisation. Volunteers were inoculated with HCV 229E, and daily nasal washings were collected. These washings were then examined for the presence of viral RNA using a single-stranded RNA probe. Nucleic acid hybridisation is shown to be a sensitive technique for the diagnosis of HCV 229E infections.