Three monoclonal antibodies (mAbs) were generated against mink leukocytes. One antibody reacted with all T lymphocytes, one with all monocytes and one had platelet reactivity. Under reducing conditions, the T lymphocyte reactive antibody immunoprecipitated 18 kDa, 23 kDa, 25 kDa and 32-40 kDa polypeptides and the platelet reactive antibody 17 kDa, 22 kDa plus two high molecular weight (> 100 kDa) polypeptides. Immunohistological studies of the mAbs were performed in order to localize the cellular distribution of the detected antigens in various organs. The T lymphocyte reactive antibody detected an antigen, which was widely distributed in the T cell area of lymph nodes and spleen and in the thymic medulla. We conclude that this antibody is an anti-CD3 mAb and suggest that the platelet reactive antibody reacts to the CD41/CD61 integrin molecule. In addition to our own mAbs, more than 100 mAbs against leukocytes of human and various animal species have been analysed for cross-reactivity to mink leukocytes. We found eight to cross-react with mink. Of particular importance was an anticanine CD11a mAb, an antihuman CD79a mAb and an antihuman bcl-2 mAb.