Inclusion Criteria:

- Patient must have multiple myeloma that has either relapsed or has high risk
cytogenetics.

- Patients with relapsed multiple myeloma following autologous stem cell
transplantation must have achieved at least partial response following additional
chemotherapy (cohort 1):

- Patients are eligible if relapse occurs with complex/high-risk cytogenetics or occurs
with normal cytogenetics but within 15 months following the autologous transplant.

- Patients with high risk cytogenetics at diagnosis must have achieved at least very
good partial response following autologous stem cell transplantation (cohort 2):

- Patients must have complex karyotype, 1q25, del17p, t4;14 and/or t14;16 by FISH
and/or del13 by karyotyping.

DONOR: Patients must have a healthy HLA matched or mismatched related or unrelated donor
who is willing to receive G-CSF injections and undergo apheresis for PBSC collection, or
undergo a marrow harvesting procedure.

1. HLA-matched related and unrelated donors Patients who have an HLA-matched related or
unrelated donor are eligible for entry on this protocol. This will include a healthy
donor who is genotypically matched at all A, B, C, DRB1 and DQB1 loci, as tested by
DNA analysis.

2. HLA- mismatched related and unrelated donors Patients who do not have an HLA-matched
donor but have a related or unrelated donor who have one antigen or one allele
mismatch at the HLA A, B, C, DRB1 or DQB1 loci, will be eligible for entry on this
protocol.

The following inclusion criteria are also required:

- Patients should be ≥ 21, < 70 years old.

- Patients may be of either gender or any ethnic background.

- Patients must have a Karnofsky (adult) or Performance Status > 70%

- Patients must have adequate organ function measured by:

Cardiac: asymptomatic or if symptomatic then LVEF at rest must be ≥ 50% and must improve
with exercise. Hepatic: < 3x ULN ALT and < 1.5 total serum bilirubin, unless there is
congenital benign hyperbilirubinemia.

Renal: serum creatinine <1.2 mg/dl or if serum creatinine is outside the normal range,
then CrCl > 40 ml/min (measured or calculated/estimated) with dose adjustment of
Fludarabine for <70ml/min.

Pulmonary: asymptomatic or if symptomatic, DLCO > 50% of predicted (corrected for
hemoglobin)

- Each patient must be willing to participate as a research subject and must sign an
informed consent form.

Exclusion Criteria:

- Patients achieving < Partial Response following preceding chemotherapy (cohort 1) or
< Very Good Partial Response following autologous stem cell transplantation (cohort
2).

- Patients with Plasma Cell Leukemia.

- Female patients who are pregnant or breast-feeding

- Active viral, bacterial or fungal infection

- Patient seropositive for HIV-I/II; HTLV -I/II

- Patients who have undergone prior allogeneic hematopoietic stem cell transplantation.

- Patients who have had a previous malignancy that is not in remission.

- Patients with known hypersensitivity to mouse proteins (murine antibodies in ISOLEX)
if receiving SBA-E- bone marrow, or chicken egg products.