The anti-CD1 monoclonal antibodies submitted to the 1st International Workshop on Leucocyte Differentiation Antigens of Cattle, Sheep and Goats were tested for their reactivity on sheep skin, thymus and lymph node and for their reactivity with sheep efferent and afferent lymph and peripheral blood. With the exception of 20-27 they all stained that same cell populations. The antibodies precipitated molecules with a heavy chain of 46,000 apparent molecular weight and a light chain of 14,000 apparent molecular weight. VPM5 and CC14 antigens were purified by affinity chromatography. All the antibodies cross-reacted with these molecules. The results show that 20-27 recognises the same molecules as the other antibodies and suggest that 20-27 is a pan CD1 monoclonal antibody and the other monoclonal antibodies are homologues of the human CD1b molecules.