Adenoviruses replicate in the mucosal surfaces of the respiratory and intestinal tracts of humans and animals. Therefore, recombinant adenoviruses are attractive live vectors for antigen delivery to induce effective mucosal immune responses. Enteric coronavirus is an important cause of neonatal diarrhoea in calves resulting in significant economic losses due to the mortality and decreased productivity of the survivors. The hemagglutinin-esterase (HE) of bovine coronavirus (BCV) encodes a major viral membrane glycoprotein that elicits BCV-neutralizing antibodies (Deregt & Babiuk, 1987). We constructed a recombinant adenovirus vector to carry the HE gene of BCV in the early transcription region 3 of the adenovirus genome (Yoo et al. 1992). Testing of recombinant human adenovirus in animals has been difficult due to the highly restricted host range. We have used cotton rats as a model to test the immunogenicity of our recombinant adenovirus vector, since they have been shown to support replication of various adenovirus including human Ads (Pacini et al 1984).