Inclusion Criteria:

          1. Patient must be above the age of 1 month as of the start date of study treatment.

          2. Patient must be scheduled to undergo allogeneic hematopoietic stem cell transplant
             (HSCT) (adults or pediatric patients) or autologous HSCT (pediatric patients only) and
             be at high risk or very high risk of developing veno-occlusive disease (VOD).

          3. Female patients (and female partners of male patients) of childbearing potential who
             are sexually active must agree to use a highly effective method of contraception with
             their partners during exposure to defibrotide and for 1 week after the last dose of
             defibrotide.

          4. Adult patients must be able to understand and sign a written informed consent. For
             minor patients, the parent/legal guardian or representative must be able to understand
             and sign a written informed consent. Assent, when appropriate, will be obtained
             according to institutional guidelines.

        Exclusion Criteria:

          1. Patient has hemodynamic instability within 24 hours before the start of study
             treatment.

          2. Patient has acute bleeding that is clinically significant within 24 hours before the
             start of study treatment.

          3. Patient used any medication that increases the risk of bleeding within 24 hours before
             the start of study treatment.

          4. Patient is using or plans to use an investigational agent for the prevention or
             treatment of VOD.

          5. Patient, in the opinion of the investigator, may not be able to comply with the safety
             monitoring requirements of the study.

          6. Patient or parent/legal guardian or representative has a psychiatric illness that
             would prevent the patient or parent/legal guardian or representative from giving
             informed consent and/or assent.

          7. Patient has a serious active disease or co-morbid medical condition, as judged by the
             investigator, which would interfere with the conduct of this study.

          8. Patient is pregnant or lactating and does not agree to stop breastfeeding.

          9. Patient has a known history of hypersensitivity to defibrotide or any of the
             excipients.

         10. Patient or parent/legal guardian or representative lacks the full mental capacity to
             understand and sign a written informed consent.

         11. Patient is receiving or plans to receive other investigational therapy during study.