In order to enumerate the T-lymphocytes in bovine peripheral blood lymphocytes (PBL) by E rosette assay, KGRBC were treated with various concentrations of 2aminoethyl-isothiouronium bromide (AET) and dextran (Dex), singly or in combination. To further standardize the assay, optimum concentration of AET-and/or Dex-treatment and incubation time for rosette forming cell (RFC) counts were determined. The levels of B-lymphocytes in the PBL were evaluated by erythrocyte-antibody (EAfc)- and erythrocyte-antibody-complement (EAC)- rosetting techniques. The PBL from 20 clinically normal Korean cattle were formed as low percentage of spontaneous E-rosette (6.7 +- 2.4 %) in control group, whereas in KGRBC treated with 0.1M AET for 20 minutes and 8 % Dex were formed as 37.3 +- 2.7 % and 45.1 +- 2.1 %, respectively. And the synergistic effects were noted no less than 66.5 +- 5.6 % when the KGRBC treated with 0.1M AET and 8 % Dex subsequently and rate of RFR did not change significantly between 3-24 hours incubation time at 4deg C, EA-and EAC-RFR were 23.3 +- 9.1 % and 23.1 +- 7.9 %, respectively. These results suggest that the KGRBC would be a useful agent for the enumeration of T-lymphocytes by E rosette assay and B-lymphocytes by EA-or EAC-rosette assay in cattle-PBL