Two- and 6-week-old chicks were inoculated with the Kagoshima-34 strain of avian infectious bronchitis virus. Serum, bile, Harderian gland, lachrymal fluid, saliva and tracheal washings were collected and their antibody content determined using neutralisation tests. The neutralising antibody (NA) in the serum and bile was detected earlier and in slightly higher concentration in the 6-week-old chicks. Although there was no marked difference in the levels of NA in other body fluids, it was detected earlier in the 6-week-old chicks. In both experiments, the clinical signs were more severe in the 2-week-old chicks. Recovery of virus from the trachea of both ages was not different but virus was recovered for longer in the lungs, kidneys and colon of the 2-week-old chicks. This is the first report wherein IBV-neutralising antibody in the bile is described.