The anemia frequently observed in lead poisoning is thought to resultfrom the shortening of erythrocyte life span in combination with inhibition of hemoglobin synthesis. However, the exact mechanism by which lead shortens the life span of red blood cells (RBCs) remains unclear. In the present study, the effects of injected lead on electrophoretic mobility, membrane sialic acid content, deformability and survival of rat RBCs were investigated in order to clarify therelationships between them. As indices of lead exposure, RBC counts, hemoglobin (Hb) levels, hematocrits (Ht), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC) and blood lead(blood Pb) levels in the rats were also examined. Exposure to lead significantlydecreased RBC counts, Hb levels, Ht, MCV and MCH. Similarly, exposure to lead significantly decreased the mobility, sialic acid content and deformability of ratRBCs. A shortening of erythrocyte survival time was also observed in the rats exposed to lead. It is speculated that decreases in membrane sialic acid content and deformability of RBCs induce a shortening of erythrocyte survival time in anemia caused by lead.