A review of 54 patients with acute leukemia in remission confirms the impression that bone marrow lymphocytosis (BML) of 20 per cent or more is not a manifestation of incomplete remission, but may be an indicator of good prognosis. This concept is particularly manifest in patients with acute lymphocytic leukemia. Eight such patients without BML have had median remissions and survivals of five and 10 months, respectively, while 30 patients with BML have had remissions and survivals of nine and 35 months.