DISEASE CHARACTERISTICS: Histologically confirmed childhood acute lymphoblastic leukemia (ALL) in second hematologic remission or greater who have relapsed: On therapy OR Within one year of discontinuation of therapy OR Greater than 1 year from discontinuation of high risk intensive therapy (matched sibling donor only) Patients with central nervous system or testicular relapse: Occurred within 18 months of diagnosis OR Following prophylactic or therapeutic cranial irradiation T cell disease with isolated central nervous system (CNS) or bone marrow relapse at any time Patients in first remission with greater than 4 weeks to achieve remission or with high risk features such as: t(4,11) t(9,22) Hypodiploidy Patients under 12 months of age in first remission with any of the following features at diagnosis: CALLA (CD10) negative white blood count (WBC) at least 100,000/mm3 Day 14 M2 or M3 bone marrow CNS disease