The peroxidase-antiperoxidase (PAP) technique was used to identify cytoplasmic immunoglobulins in the accessory sex glands of 15 normal bulls and 13 bulls with inflammation of the ASG. Immunoglobulin containing cells (ICC) of the types IgA, IgM, total IgG, IgG1 and IgG2 were measured and their percentages expressed. In accessory sex glands from normal bulls, IgA containing cells were the most frequent in prostate and bulbourethral glands (86.7% and 86.1%, respectively of all ICC present) whereas in the ampulla, IgG containing cells comprised 78.6% of the ICC. IgG1 and IgG2 containing cells were present in all the accessory sex glands in approximately equal numbers. Frequencies of IgM containing cells in the ampulla, prostate and bulbourethral glands were 6.3%, 4.0% and 3.7%, respectively. Although all isotypes of ICC were present in the seminal vesicle, the very low number precluded accurate quantification. In inflamed ampulla, seminal vesicle, bulbourethral gland and colliculus seminalis, IgG containing cells were the most frequent ICC with values of 66.2%, 83.0%, 69.0% and 53.5%, respectively; IgA containing cells were the second in prevalence with values of 21.5%, 10.3% 19.3% and 40.5%, respectively. The contribution of ICC to the locally protective immunoglobulins in accessory sex gland secretions is discussed.