Among all mAb submitted to the first porcine CD workshop, based on FCM analyses six mAb could be identified to recognize the porcine CD8 analogue (workshop Nos. 004, 051, 052, 053, 108 and 109). In immunoprecipitation studies three mAb (Nos. 004, 108 and 109) recognized an antigen with an apparent molecular mass of about 35 kDa under reducing conditions and about 70 kDa under non-reducing conditions. The molecular masses of the antigens recognized by the three other mAb (Nos. 051, 052 and 053) are still unknown. Epitope analyses performed by blocking experiments led to the determination of two CD8 epitopes: CD8a and CD8b. CD8a is recognized by mAb Nos. 004, 051 and 052, and CD8b by Nos. 053, 108 and 109.