Erythrocyte, hemoglobin, packed-cell volumes, and total and differential leucocyte counts from wild caribou are compared with values determined for captive animals maintained on a high plane of nutrition. The mean corpuscular hemoglobin of lactating female caribou, about 30%, differed from the normal value of 34%, suggesting that some of the wild caribou may suffer from hypo-chromic anemia. Plasma electrolytes and calcium and phosphorus levels were slightly lower in wild than captive caribou. The blood urea nitrogen level was about 28% higher in captive than wild caribou, because of differences in protein intake.