Thirty-six beagle dogs were divided into three hematologically similar groups of six males and six females each. The dogs of one group acted as controls and were fed only the basic diet. The dogs of the other two groups had lead acetate added to their diets, those of one group receiving 100 ppm of lead by weight, those of the other group, 500 ppm for 30 weeks followed by 1000 ppm for 16 weeks. By the end of 46 weeks, both lead-treated groups had accumulated burdens of lead as demonstrated by increases in blood and urine lead concentrations, increased urine δ-aminolevulinic acid excretion, and decreased red cell ALA dehydrase activity. At this time a two-step withdrawal of one-half the estimated blood volume from each dog resulted in a 30 to 40% reduction in hemoglobin concentration, red cell count, and hematocrit ratio. The recoveiy curves of the hemoglobin concentration, red cell count, and hematocrit ratio were not affected by the presence of the lead.