CLL is the most common mature B-cell leukemia in the Western hemisphere and makes up 30% of all leukemias. It mainly affects middle-aged and elderly patients with a male predominance. The neoplastic cells are mainly in the blood and bone marrow. CLL is asymptomatic in most patients and often detected incidentally on complete blood counts. The diagnosis requires absolute mature lymphocytosis of ≥ 5.0 x 109/L sustained for at least 3 months. The smears show a monotonus population of lymphoid cells which have scant cytoplasm, small, round nuclei with condensed chromatin and inconspicuous nucleoli. During the smear preparation, the leukemic cells easily get disrupted creating smudge cells. They consist largely of nuclear material. One smudge cell can be seen near the upper right corner of this image.