We present the case of a 12-year-old boy with T-cell acute lymphoblastic leukemia (ALL) who developed a chronic hepatitis-B virus (HBV) infection during the consolidation phase of chemotherapy and was unable to receive further therapy because of hepatotoxicity. Recombinant alpha-2a interferon (alpha-IFN) treatment (5 million units/m2 per dose, three times a week) was started for chronic HBV infection at the end of the sixth month, and vincristine (1.5 mg/m2) was administered once a month as the only well-tolerated chemotherapeutic agent. During follow-up, the dose of alpha-IFN was increased to 10 million units/m2 three times a week, depending on the patient's laboratory data. Three months later, elimination of HBe Ag and HBV DNA and seroconversion from HBe Ag to HBe Ab occurred. The duration of alpha-IFN therapy was prolonged to 18 months, since other chemotherapeutic agents caused hepatotoxicity whenever they were tried and alpha-IFN treatment can be used in children with refractory T-cell leukemia in view of its antitumor effect. Our patient has now been in complete remission for 4 years. Alpha-IFN therapy should be considered as an alternative treatment for patients with T-cell ALL who cannot receive chemotherapy because of HBV infection or for any other reasons.