Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically proven high-risk hematologic malignancy

- Acute non-lymphocytic leukemia (ANLL) after induction failure, or in first
complete remission (CR) with high-risk features, including any of the following:

- Stem cell or biphenotypic classification (AML-M0)

- Erythroleukemia (AML-M6)

- Acute megakaryocytic leukemia (AML-M7)

- Cytogenetic markers indicative of poor prognosis

- Failure to achieve CR after standard induction therapy

- Acute lymphocytic leukemia (ALL) or ANLL in relapse or second or subsequent
remission

- Chronic myelogenous leukemia (CML) in chronic or accelerated phase

- Patients with CML in blast crisis are eligible after reinduction
chemotherapy places them in chronic phase

- High-risk ALL in first CR with high risk defined by presence of t(4;11), t(9;22)
translocation, hyperleukocytosis (initial WBC greater than 30,000/mm^3), or
failure to achieve CR by day 28 after standard induction

- No T-cell ALL or t(8;14) positive B-cell ALL in first remission with
hyperleukocytosis

- Myelodysplastic syndrome by peripheral blood smear and bone marrow examination

- Refractory to medical management OR

- Cytogenetic abnormalities predictive of transformation into acute leukemia
including 5q-, 7q-, monosomy 7, and trisomy 8 OR

- Evidence of evolution to AML (e.g., refractory anemia with excess blasts
(RAEB) or RAEB in transformation)

- Multiple myeloma, non-Hodgkin's lymphoma (NHL), ANLL, or ALL with recurrent
disease after autologous stem cell transplantation (SCT)

- At least 3 months since prior autologous SCT

- Hodgkin's lymphoma, NHL, or multiple myeloma beyond first CR or primary
induction failures whose disease has demonstrated sensitivity to
pre-transplantation cytoreduction (defined as greater than 50% reduction in
tumor burden)

- Mantle zone NHL allowed after induction therapy

- Myeloproliferative disorder that is non-responsive to medical management and
requires allografting, unless evidence of grade 3 or worse myelofibrosis on
marrow biopsy OR

- Histologically proven acquired severe aplastic anemia (SAA) that is recurrent or
unresponsive after anti-thymocyte globulin and/or cyclosporine

- SAA defined by at least 2 of the following conditions:

- Granulocyte count less than 500/mm^3

- Platelet count less than 20,000/mm^3

- Absolute reticulocyte count less than 20,000/mm^3 after correction for
hematocrit

- Ineligible for full ablative conditioning due to any of the following conditions:

- Prior extensive therapy (more than 2 salvage chemotherapy regimens and/or
autologous transplantation)

- Over age 55 OR

- Under age 55 with comorbid disease (e.g., suboptimal cardiac, pulmonary, or
renal function and/or prior life-threatening infection)

- HLA-A, B, and DR phenotypically identical sibling donor OR

- HLA-A, B, and DR identical genetically matched unrelated donor

- No ANLL in first CR (less than 5% blasts in marrow) with translocations t(8;21) and
inv(16) unless failed first-line induction therapy OR

- No ANLL in first CR (less than 5% blasts in marrow) with translocations t(15;17)
abnormality unless failed first-line induction therapy OR molecular evidence of
persistent disease

- No active CNS disease

PATIENT CHARACTERISTICS:

Age:

- 0 to 70

Performance status:

- Zubrod 0-1

- Karnofsky 80-100%

Life expectancy:

- At least 3 months

Hematopoietic:

- See Disease Characteristics

Hepatic:

- ALT/AST no greater than 4 times normal

- Bilirubin no greater than 2.0 mg/dL

Renal:

- See Disease Characteristics

- Creatinine clearance at least 50 mL/min

Cardiovascular:

- See Disease Characteristics

- Shortening fraction or ejection fraction at least 40% of normal for age by
echocardiogram or radionuclide scan

- No clinically significant comorbid illnesses (e.g., myocardial infarction or
cerebrovascular accident)

Pulmonary:

- See Disease Characteristics

- FVC and FEV_1 at least 60% of predicted for age

- DLCO at least 60% of predicted for adults

Other:

- No severe neurosensory symptoms (i.e., peripheral neuropathy)

- HIV negative

- Active infection allowed if controlled by appropriate drug therapy

- Not pregnant or nursing

- Negative pregnancy test

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- See Disease Characteristics

Chemotherapy:

- See Disease Characteristics

Endocrine therapy:

- Not specified

Radiotherapy:

- Not specified

Surgery:

- Not specified

Other:

- Recovered from prior therapy

- No concurrent investigational agents unless approved by protocol investigators