Inclusion Criteria:

- Age greater than18 years at the time of signing the informed consent form.

- Able to adhere to the study visit schedule and other protocol requirements.

- MDS or MDS/AML

- Patients must not have received any other treatment for their disease, including
hematopoietic growth factors, within three weeks of beginning the trial

- ECOG performance status of 0, 1, or 2 at study entry

- All study participants must be registered into the mandatory RevAssist® program, and
be willing and able to comply with the requirements of RevAssist®.

- Patients must have no clinical evidence of CNS or pulmonary leukostasis, disseminated
intravascular coagulation, or CNS leukemia.

- Subjects must agree to use appropriate contraception.

Exclusion Criteria:

- Any serious medical condition, laboratory abnormality, or psychiatric illness that
would prevent the subject from signing the informed consent form.

- Pregnant or breast feeding females. (Lactating females must agree not to breast feed
while taking lenalidomide).

- Any condition, including the presence of laboratory abnormalities, which places the
subject at unacceptable risk if he/she were to participate in the study or confounds
the ability to interpret data from the study.

- Use of any other experimental drug or therapy within 21 days of baseline.

- Known hypersensitivity to thalidomide.

- The development of erythema nodosum if characterized by a desquamating rash while
taking thalidomide or similar drugs.

- Any prior use of lenalidomide except for MDS patients with del 5q31.1 abnormalities..

- Concurrent use of other anti-cancer agents or treatments.

- Patients may not have received prior AML induction chemotherapy or stem cell
transplant. However, patients with secondary MDS who have received a stem cell
transplant for other indications (eg lymphoma, multiple myeloma) will be eligible.