DISEASE CHARACTERISTICS: Histologically proven chronic myeloid leukemia (CML) in first chronic phase or with cytogenetic but not hematologic evidence of acceleration (clonal evolution) Availability of 6 antigen (A, B, and DR loci) HLA identical sibling donor Eligible for randomization to donor lymphocyte infusion (DLI) if: Residual Ph+ cells by cytogenetics or FISH or hematologic or clinical evidence of CML AND No graft versus host disease requiring immunosuppressive therapy within the past 2 weeks AND Evidence of donor hematopoiesis after completion of transplantation Ineligible for randomization to DLI if: Blast transformation of CML OR Prior interferon alfa for relapse after completion of transplantation