Patients with acute lymphoblastic leukemia (ALL) are stratified into three risk categories. These categories serve to determine therapeutic management and prognosis. Categories are based on whether the patient’s cerebrospinal fluid (CSF) has pleocytosis and/or blasts. Studies on CSF obtained from patients with various neurologic diseases have shown decreases in leukocyte counts through time, but no studies have been done specifically involving ALL patients. Moreover, delays between CSF collection and processing with Cytocentrifuge (Cytospin) are common at our institution. We determined the effect of delay processing on leukocyte counts in CSF from ALL patients by performing differential count at different time intervals between collections and processing. CSF was subjected to Cytospin at three-time intervals after collection. Leukocyte counts were performed using light microscopic examination. Leukocyte survival was calculated for each leukocyte subtype. Different time interval groups were compared using Wilcoxon Signed-Rank Test, and p values of less than 0.05 were considered significant. The median percentage of survival of total leukocytes at two hours and four hours are 14% and 12%. The (define median percentages and its statistical significant- please see attached explanation) median percentages of survival for the specific leukocyte subtypes are as follows: for lymphocytes, 4% and 15%; for granulocytes and monocytes, 0% for both; for blasts, 0% and 212%. Five cases were blast-positive, three of which showed a persistence of blasts at the fourth hour. Wilcoxon Matched-Pair Test showed that there was a significant difference in the 15-minute group versus the 2-hour group, and versus the 4-hour group, in the leukocyte subsets except for blasts. We have shown that for pediatric ALL patients, there is a decline in CSF leukocyte survival with the time. Limited number of blast-positive cases prevents us from making a similar statement for blasts. Our observation, where blasts persisted in 3 out 5 cases after four hours, may suggest them to be more resilient than normal leukocytes, but a larger blast-positive subset is needed.