Background: ALL is a malignancy of B or T lymphoblasts which is characterized by unrestrained spread of abnormal, immature lymphocytes and their progenitors which results in the replacement of bone marrow and other lymphoid organs subsequently. Methods: This study was a observational cross sectional study conducted at the Department of Hematology, in Bangabandhu Sheikh Mujib Medical University, Shahbag, Dhaka, Bangladesh. The study period was from October 2019- September 2020. The sample size for this study was 100. Result: Most of the respondents 53(53%) were from <20 years and the mean age was 30±11.18. The female was 68(68%) and male was 32(32%). Fever was found in 100% cases and Progressive pallor in 98%. Bony tenderness was found in 58 cases and followed by Splenomegaly 48, Lymphadenopathy in 46, Oral ulcer in 46, Hepatomegaly in 36. The range of Total WBC count (x109/L) was (6-435) and the Mean±SD was 52.51±78.70 and followed by Hb% (gm/dl) was (4.1-13.4) and 9.25±1.49, Platelet (x109/L) was (5-20000) and 505.20±2815.29. S. uric acid (mg/dL) was (1.40-30.03) and 5.76±4.61. S. inorganic phosphate (mg/dL) was (2.30-7.70) and 4.19±1.20. S. potassium (mmol/L) (2.50-5.40) and 3.92±0.56. S. calcium (mg/dL) was (1.10-11.80) and 8.33±2.08. S. creatinine (mg/dL) was (0.19-3.59) and 89±0.55. In 72% TLS was absent and in 28% was present. Conclusions: Rapid spread of TLS often causes severe toxic effects on organs, which leads to renal impairment, epilepsy, cardiac arrhythmias, pulmonary edema, and even death.