We evaluated the efficiency of a new porous type leukocyte removal filter for red cell blood components, Terumo Imuguard III-RC, in the rapid transfusion conditions. One leukocyte removal filter was used for 2 units of RC-M.A.P (red cell mannitol-adenine-phosphate). Filtration methods employed were gravity infusion, high pressure infusion (300 mmHg), pumping infusion and 20 ml.min-1 infusion under high pressure (300 mmHg). Blood samples were taken before and after the filtration to measure white blood cell (WBC), red blood cell (RBC) and platelet content. Blood samples before filtration and after filtration with WBC excluded, were examined by automated hematology analyzer (Coulter counter STKS-Retic). WBC after filtration was counted by the hemacytometer method using Nageotte Chamber. The removal rate of WBC was found to be more than 99.99% and residual WBC content was less than 4 x 10(4) with every method. The recovery rate of RBC was not significantly decreased in all filtration methods. The removal rate of platelet was equal in all filtration methods. In conclusion, Imuguard III-RC could be useful for effective homologous blood transfusion.