Abstract
Summary Punned suspensions of human blood lymphocytes in 50% normal human serum were incubated at 37°C in small test tubes and the number of viable lymphocytes were counted weekly with a phase contrast microscope. The tubes were not shaken and the medium not changed. In suspensions from hematologically normal individuals, 24% of the lymphocytes survived 2 weeks and 5%, 3 weeks. In blood cell suspensions derived from 13 patients with chronic lymphocytic leukemia, 29% of the lymphocytes survived 3 weeks and some of the cells survived 7 weeks. The percentages of leukemic lymphocytes that survived 3 weeks varied considerably for the 13 patients and were directly correlated with the absolute lymphocyte counts of the patients.