Inclusion Criteria:

1. Patients will be 16 years of age or older.

2. Patients must have relapsed/refractory leukemias for which no standard therapies are
anticipated to result in a durable remission (longer than 3 months). Patients with
poor-risk myelodysplasia (MDS) [i.e. refractory anemia with excess blasts (RAEB-1 or
RAEB-2) by World Health Organization (WHO) classification] and chronic myelomonocytic
leukemia (CMML) are also candidates for this protocol. Relapsed/refractory leukemias
include acute myeloid leukemia (AML), acute lymphocytic leukemia (ALL), or chronic
myelogenous leukemia (CML) in blastic phase.

3. Continued from #2: Elderly patients with AML who are not eligible for frontline
standard therapy, or who refuse to be treated with intensive chemotherapy, may be
eligible. The phase II portion of the study will enroll patients with AML, MDS, and
ALL. Patients with CML and CMML will not participate in the phase II portion of the
study. Patients who are being considered for stem cell transplant are also eligible
for this protocol.

4. Eastern Cooperative Oncology Group (ECOG) performance status of 0-3.

5. Women of child-bearing potential (i.e., woman has not been naturally postmenopausal
for at least 24 consecutive months or not surgically sterile) must use acceptable
contraceptive methods (abstinence, intrauterine device [IUD], oral contraceptive or
double barrier device), and must have a negative serum or urine pregnancy test within
2 weeks prior to beginning treatment on this trial. Sexually active men must also use
acceptable contraceptive methods for the duration of time on study. Men and women
must maintain effective contraception until 4 weeks after the last dose of drug is
administered.

6. Must be able and willing to give written informed consent.

7. In the absence of rapidly progressing disease, the interval from prior treatment to
time of study drug administration should be at least 2 weeks for cytotoxic agents, or
at least 5 half-lives for noncytotoxic agents. If the patient is on hydroxyurea to
control peripheral blood leukemic cell counts, the patient must be off hydroxyurea
for at least 24 hours before initiation of treatment on this protocol. Persistent
clinically significant toxicities (any grade 2 or worse toxicities, non-hematologic
or hematologic) from prior chemotherapy must not be greater than Grade 1.

8. Patients must have the following clinical laboratory values unless considered due to
leukemic organ involvement: 1) Serum creatinine 1.5 times the upper limit of normal unless considered due to Gilbert's syndrome; 3)
Alanine aminotransferase (ALT), or aspartate aminotransferase (AST) upper limit of normal unless considered due to organ leukemic involvement.

9. Patients with active Central Nervous System (CNS) disease are included and will be
treated concurrently with intrathecal therapy.

10. Phase II Portion: All above criteria apply. After the phase I portion, patients
eligibility will be for only 3 disease categories which will accrue in parallel: 1)
AML, 2) MDS, and 3) ALL.

Exclusion Criteria:

1. Uncontrolled intercurrent illness including, but not limited to uncontrolled
infection (i.e. persistent fever, clinical deterioration), acute congestive heart
failure and exacerbation, cardiac arrhythmia, chronic liver disease, or psychiatric
illness/social situations that would limit compliance with study requirements.

2. Active heart disease including myocardial infarction within previous 3 months,
unstable angina, arrhythmias not controlled by medication, or uncontrolled congestive
heart failure. Patients with New York Heart Association (NYHA) class 3 or 4 are
excluded.

3. Patients receiving any other standard or investigational treatment for their
hematologic malignancy, except as permitted under Inclusion #9 above.

4. Pregnant or breast feeding females are excluded because the effects of bendamustine
on a fetus or nursing child are unknown.