The applicability of the immunoperoxidase (IP) technique in unfixed-fresh tracheal organ cultures (TOCs) was investigated for rapid detection of infectious bronchitis virus (IBV). For this purpose, TOCs prepared from one-day-old SPF chicks were inoculated with IBV M41 strain in serial dilutions. IBV antigen detected by IP technique in TOCs 18 h postinoculation. IP staining was observed before siliostasis in all dilutions. The IP technique was also applied to detect IBV antigen in formalin-fixed, paraffin-embedded sections of TOCs inoculated with IBV M41 strain. Viral antigen was also detected in these sections. Histopathological examinations of IBV M41 infected tracheal rings showed loss of cilia, flattening of lamina epithelialis, and rounding and desquamation of epithelial cells.