Aim. To present the results of treatment in adult patients with acute T-lymphoblastic leukemia (T-ALL) according to the ALL-2009 protocol of the Russian Acute Leukemia Study Group, the basic principle of which is continuation of cytostatic treatment, early switch from prednisolone to dexamethasone, and long-term use of L-asparaginase. Subjects and methods. The results of diagnosis and treatment were analyzed in 70 patients with different immunological variants of T-ALL treated in the Russian multicenter trial. Results. Out of the 70 patients with T-ALL, its early immunotype was determined in 32 (45.7%) cases, the thymic and mature immunotypes were found in 31 (44.3%) and 7 (10%) cases, respectively. The median age of the patients with T-ALL was 28 (ranged from 15 to 54) years; men were twice more than women (48 and 22, respectively). Bone marrow lesion was noted in all the patients with early T-ALL and in 80% of the patients with thymic and mature T-ALL. The enlarged mediastinum was significantly more frequently detected in mature T-ALL (100%) than in its early (53.4%) and thymic (60.7%) variants. Therapeutic effectiveness was evaluated in 58 patients. An analysis was made in January 2013. Induction therapy resulted in complete remission in 49 (84.5%) patients. The refractory course of the disease was recorded in 5 (8.6%) cases; early death was in 4 (6.9%). The rate of complete remission in thymic T-ALL, unlike in the early (72%) and mature (71.4%) variants, was significantly higher (100%) due to the absence of resistant forms and early mortality. Moreover, it should be noted that only the patients with early T-ALL (16%) died during the induction phase. In the patients with different variants of T-ALL, the overall and relapse-free survival rates were not significantly different, accounting for 67.2 and 76.2%, respectively. Multivariate analysis revealed no prognostically unfavorable factors that determined long-term results. Conclusion. The ALL-2009 protocol is reproducible in any regions of the Russian Federation and highly efficient in treating patients with T-ALL.