Granulocytes include neutrophils (bands and segs), eosinophils, and basophils. In evaluating numerical aberrations of these cells (and of any other leukocytes), one should first determine the absolute count by multiplying the per cent value by the total WBC count. For instance, 2% basophils in a WBC of 6,000/uL gives 120 basophils, which is normal. However, 2% basophils in a WBC of 75,000/uL gives 1500 basophils/uL, which is grossly abnormal and establishes the diagnosis of chronic myelogenous leukemia over that of leukemoid reaction with fairly good accuracy. Neutrophilia is seen in any acute insult to the body, whether infectious or not. Marked neutrophilia (>25,000/uL) brings up the problem of hematologic malignancy (leukemia, myelofibrosis) versus reactive leukocytosis, including leukemoid reactions. Laboratory work-up of this problem may include expert review of the peripheral smear, leukocyte alkaline phosphatase, and cytogenetic analysis of peripheral blood or marrow granulocytes. Without cytogenetic analysis, bone marrrow aspiration and biopsy is of limited value and will not by itself establish the diagnosis of chronic myelocytic leukemia versus leukemoid reaction. Smokers tend to have higher granulocyte counts than nonsmokers. The usual increment in total wbc count is 1000/5L for each pack per day smoked. Repeated excess of bands in a differential count of a healthy patient should alert the physician to the possibility of Pelger-Huet anomaly, the diagnosis of which can be established by expert review of the peripheral smear. Neutropenia may be paradoxically seen in certain infections, including typhoid fever, brucellosis, viral illnesses, rickettsioses, and malaria. Other causes include aplastic anemia, aleukemic acute leukemias, thyroid disorders, hypopitituitarism, cirrhosis, and Chediak-Higashi syndrome. Eosinophilia is seen in allergic disorders and invasive parasitoses. Other causes include pemphigus, dermatitis herpetiformis, scarlet fever, acute rheumatic fever, various myeloproliferative neoplasms, irradiation, polyarteritis nodosa, rheumatoid arthritis, sarcoidosis, smoking, tuberculosis, coccidioidomycosis, idiopathicallly as an inherited trait, and in the resolution phase of many acute infections. Eosinopenia is seen in the early phase of acute insults, such as shock, major pyogenic infections, trauma, surgery, etc. Drugs producing eosinopenia include corticosteroids, epinephrine, methysergide, niacin, niacinamide, and procainamide. Basophilia, if absolute (See above) and of marked degree is a great clue to the presence of myeloproliferative disease as opposed to leukemoid reaction. Other causes of basophilia include allergic reactions, chickenpox, ulcerative colitis, myxedema, chronic hemolytic anemias, Hodgkin's disease, and status post-splenectomy. Estrogens, antithyroid drugs, and desipramine may also increase basophils. Basopenia is not generally a clinical problem