Inclusion Criteria:

- Patients must be 18 years to 70 years of age, inclusive.

- Biopsy confirmation of GVHD is strongly recommended, to exclude patients presenting
with diarrhea or abnormal liver function tests caused by infection.

- Patients must have failed to respond to steroid treatment (methylprednisolone
[≥1mg/kg/day] or equivalent) for Grades C-D acute GVHD.

- Prochymal must be administered not longer than 14 days after the initiation of
systemic steroid therapy for acute GVHD.

- Prochymal must be administered either before or at the same time any additional GVHD
therapy is administered

- Patients must have an adequate renal function as defined by Cockroft-Gault
equation:Calculated creatinine clearance (CrCl) > 30mL/min

- Patients who are women of childbearing potential, must be non-pregnant, not
breast-feeding, and use adequate contraception. Male patients must use adequate
contraception.

Exclusion Criteria:

- Patient has stage 3 or 4 liver GVHD, bilirubin >6 mg/dl.

- Patient has stage 4 GI-GVHD.

- Patient has any underlying or current medical condition that would interfere with the
evaluation of the patient including uncontrolled infection, sepsis, organ failure,
etc or any medical condition that has a high probability of causing death in less
than 30 days.

- Patient may not receive any other investigational agent (not approved by the FDA for
any indication) concurrently for the duration of the protocol.

- Patient has evidence of a pulmonary infiltrate or diffuse alveolar hemorrhage and
must not be likely to require more than 2L of oxygen via face mask or an estimated
FiO2of 28% via other delivery methods in order to sustain an O2 saturation of 92%
during the next 3 days.

- Patient has a known allergy to bovine or porcine products

- Patient has a medical history of a solid tumor disease.