We gave preoperative blood transfusions to 37 patients with rheumatoid arthritis (RA) and 35 patients with osteoarthritis (OA), including some whose baseline hemoglobin level was less than 10 g/dl. Transfusion packs can preserve whole blood containing citrate phosphate dextrose (CPD) for 3 weeks. The baseline hemoglobin level of RA cases was 10.4 g/dl (range 8.4-13.1 g/dl), and that of OA cases was 11.9 g/dl (range 10.4-15.0 g/dl). By collecting 200-400 g every week before the operation, the total was 800-1200 g. Erythropoietin was given to patients intramuscularly when their hemoglobin was less than 13 g/dl after blood had been collected. Hemagglutination, with diameters of more than 1 cm, made filter occlusions in 11 RA cases (30%) and one OA case (3%) (P << 0.0031) after retransfusion. There were no differences between hemagglutination patients (agglutination group) and nonhemagglutination patients (nonagglutination group) regarding baseline C-reactive protein (CRP), white blood cells, platelets, or fibrinogen. We could not predict the formation of macrohemagglutination in the packs collected during the clinical course. In RA cases, allogenic transfusions were performed for four cases (36%) in the agglutination group and for one case (12%) in the nonagglutination group. Preoperative transfusion for the RA patients showed hemagglutination in some cases, and highlighted the need for modifications to reduce these hemagglutinations.