A 2-year-old Holstein cow developed multiple cutaneous masses, up to 10 cm in diameter, over the neck and trunk. The animal also had neoplastic lesions in internal organs, and epitheliotropism was observed not only in the skin but also in the conjunctiva, mammary glands, trachea, abomasum, small intestine, gall bladder, uterus and urinary bladder. Moreover, the neoplastic cells showed preferential homing to T-zones of lymphatic tissues. Because the lymphoma cells were positive for CD3 but not CD79a, and a few were CD2- or WC1-positive, this lymphoma was thought to be of gammadelta T-cell origin. Helicobacter -like organisms, found in the abomasum and small intestine, were considered to be associated with the severe neoplastic involvement of these organs, on the basis of the intense immunolabelling for major histocompatibility complex class II in the epithelial cells, and the presence of increased numbers of apparently normal intraepithelial T lymphocytes.