Using hyperimmune rabbit sera to BHV1, ID and CIEP tests detected one antigen in BHV1 infected cell culture harvests. In nasal and ocular secretions collected from experimentally infected cattle during the early course of clinical disease two and one BHV1 antigens were detected by the ID and CIEP tests respectively. In specimens collected from eight cattle for 10 days after the onset of pyrexia the ID test demonstrated precipitating antigens in 22/35 ocular secretions and 43/60 nasal secretions, whereas the CIEP detected antigens in 40/64 ocular secretions and 44/69 nasal secretions. The antigens were thermostable, being detectable by CIEP 14 days and seven days after storage at 4 degrees C and room temperature respectively.