Introduction: Acute lymphoblastic leukemia (ALL) is a malignant transformation and proliferation of lymphoid progenitor cells in the bone marrow, blood and extramedullary sites. While 80% of ALL occurs in children, it represents a devastating disease when it occurs in adults. Aims: To study morphological changes in bone marrow in treated cases of Acute Lymphoblastic Leukemia. Method and material – Prospective study, carried out in Department of Pathology from January 2016 to December 2018. A total of 80 cases were studied. Bone marrow aspiration done and smears were studied in all the treated cases of acute lymphoblastic leukemia. Result – bone marrow revealed hypocellular marrow in 70 % cases, Normocellular marrow in 26% cases, 4% show Hypercelluar marrow. Dyserythropoiesis and dysmegakaryopoiesis noted in 07 (8.75%) treated cases. Only 04% cases show increased % of blast (residual disease) after completion of treatment. Conclusion – A bone marrow aspiration after completion of treatment provides information whether patient has achieved remission or still has residual leukemia. It also helps in assessing dysplastic changes in all three cell line due to treatment.