Inclusion Criteria:

- Patients with CML, AML, MDS or ALL relapsed after related or unrelated donor
allogeneic marrow transplantation.

- Patients must be within one year of identification of relapse or if beyond that time
period, must have some evidence of donor DNA by RFLP or cytogenetics.

- Patients may have evidence of relapse based on molecular, cytogenetic or morphologic
criteria.

- CML patients must have cytogenetic evidence of relapse or if Ph negative to start,
obvious evidence of relapse other than minimal residual disease.

- Patients must have <30% marrow blasts on a marrow biopsy performed within two weeks
of the first donor lymphocyte infusion.

- Patients with >30% blasts can become eligible for donor lymphocytes after reinduction
with any standard therapy regimen.

- Patients with AML, MDS or ALL achieving a CR with standard therapy regimens are
eligible for this protocol.

- Patients who relapse with their initial disease or develop a second malignancy after
related or unrelated donor allogeneic marrow transplantation with other initial
diagnoses (such as but not limited to CLL, lymphoma, myeloma, juvenile CML, sarcoma,
breast cancer) may also be included in this protocol. Patients will be eligible with
or without other adjunct chemotherapy or radiation therapy. Post-transplant
lymphomas (often referred to as EBV-associated lymphomas) will be eligible for donor
leukocyte infusions on this protocol. Treatment with donor leukocytes under this
protocol is restricted to malignant diseases only. Graft failure or relapse of
non-malignant disorders is excluded from receiving donor leukocyte infusions on this
protocol. Autologous transplant patients who relapse are not eligible for this
protocol. Patients with malignant diseases amenable to other curative therapy are
not eligible (i.e. skin cancers).

Exclusion Criteria:

- Patients with concurrent signs of acute or chronic graft-versus-host disease
requiring ongoing treatment at the time of relapse will be ineligible.

- Patients with >30% marrow blasts at the time of therapy will be ineligible.

- Patients on prednisone, cyclosporine, Imuran or other immunosuppressive medications
are not eligible until these medications are discontinued for at least 2 weeks
without a flare of GVHD.

- CML patients in complete cytogenetic remission who are bcr/abl positive by PCR only
are not eligible.