Absolute blood leukocyte counts were determined in 291 normal individuals (226 Caucasian and 65 Negro), using modern, electronic leukocyte counting methods. Two hundred cell differential counts of coverslip smears stained with Wright’s stain were done. Normal mean values and 95% limits expressed as cells per cu. mm. were: band neutrophils 500 (100 to 2,100); segmented neutrophils 3,000 (1,100 to 6,050); total neutrophils 3,650 (1,830 to 7,250); lymphocytes 2,500 (1,500 to 4,000); monocytes 430 (200 to 950); eosinophils 150 (0 to 700); basophils 30 (0 to 150). No clinically significant differences between Negroes and Caucasians were found.