Five mAbs out of a total of 189 submitted to the Second Workshop were shown to be similar when statistical analyses of flow cytometry data were performed. For the duration of the workshop the five mAbs were assigned to temporary cluster TC35. The mAbs precipitated two polypeptides by SDS-PAGE under reducing conditions. One had an M(r) of 115 kDa, the other an M(r) of 39 kDa. The antigen recognized was present on thymocytes, a subpopulation of CD2+ T cells and a major subpopulation of B cells. The antigen is upregulated after long-term activation with concanavalin A. It is proposed that the mAbs in TC35 should be regarded as a single cluster identifying a novel leukocyte differentiation antigen in cattle. These mAbs were accepted as a new workshop cluster BoWC10.