Serum lactate dehydrogenase (LDH) level was estimated in 44 childhood (age range 1-15 years) acute lymphoblastic leukemia (ALL) on admission, day 14 and day 29 of induction. Another 25 children without ALL were included as control. On admission, the level of serum LDH was significantly high in ALL cases than control (p<0.001). Total WBC count was significantly decreased along with serum LDH level at day 14 and day 29 of induction (p<0.001). A significant rise of platelet count was observed at day 29 of induction in relation to significant decrease of serum LDH level (p<0.001). A significant decrease of peripheral and bone marrow blast cell percentages were also observed at day 29 of induction along with significant decrease level of serum LDH (p<0.001). So, the measurement of serum LDH level can be accepted as an enzymatic tool for presumption of childhood ALL and the response to chemotherapy during induction of remission.