Background: The identification of immunophenotype subgroups is very important for the diagnosis and prognosis of acute lymphoblastic leukemia(ALL). Material and Methods: The study included 105 children with ALL(65 males, 40 females; mean age 5.9±3.8 years) who were treated TR-ALL 2000(modified) BFM treatment protocol. Results: The distributions of EGIL classification were pro-B ALL(n=1), common B ALL(n=46), pre-B ALL(n=40), pre-T ALL(n=8), cortical T ALL(n=6), and mature T ALL(n=4). Leukocyte≥100,000/mm³, lymphadenopathy≥2 cm, mediastinal involvement were commonly identified in T ALL group. T ALL had a poor response to chemotherapy according to 8th-day peripheral circulation blast counts and 15th-day bone marrow aspiration(BMA) blast counts. The recurrence, mortality, and death rate in the induction period of treatment were frequently detected in T ALL group. The variables that had prognostic potential, as indicated by univariate analyses, were leukocyte count, hepatomegaly, splenomegaly, and lymphadenopathy at the time of diagnosis, 8th-day steroid response, 15th-day BMA response, risk group, recurrence, and immunophenotyping. Multivariate Cox regression analysis demonstrated that only the leukocyte count(HR 2.51, p < 0.001) was a predictor of prognosis. Conclusion: Immunophenotyping may be effective in the diagnosis and prognosis of ALL, identification of risk groups, and in risk-based treatment planning. T ALL had a poor prognosis.