The leukocyte count is a valuable part of the laboratory evaluation of the patient. Disposable pipets which are now available provide automatic measuring and easy mixing, and results are comparable to those obtained with glass pipets. 1 Errors in determining the total leukocyte count vary from 7% to 20%. If the count is very high, an erythrocyte pipet should be used and the necessary correction for dilution made. Appropriate corrections must also be made when nucleated erythrocytes are present in considerable number since the nuclei of these cells are not lysed by leukocyte diluting fluids. Counts done on capillary blood may be higher by 1,000 to 1,500/cu mm than those done on venous blood. This is probably due to local stasis of leukocytes. Differential count of leukocytes is absolutely essential for proper interpretation of the total leukocyte count. The white blood count (WBC) is high shortly after birth and fluctuates