Inclusion Criteria:

1. Patients should have completed their chemotherapy 3 months prior to start of treatment with lenalidomide and not more than 9 months prior to treatment initiation.
2. Patients with CLL/Small Lymphocytic Lymphoma (SLL) that achieve a complete or stable partial remission after combination of chemotherapy. Patients in complete remission need to have documentation of residual disease by immunophenotyping and/or PCR molecular testing.
3. Eastern Cooperative Oncology Group (ECOG)/World Health Organization (WHO) status of 0-2.
4. Adequate renal and hepatic function (creatinine equal to or less than 2mg/dL - total bilirubin equal to or less than 2).
5. Females of childbearing potential (FCBP). A female of childbearing potential is a sexually mature woman who: 1) has not undergone a hysterectomy or bilateral oophorectomy; 2) or has not been naturally postmenopausal for at least 24 consecutive months (has NOT had menses at any time in the preceding 24 consecutive months).
6. FCBP must have a negative serum or urine pregnancy test with a sensitivity of at least 50 mIU/mL within 10-14 days prior to and again within 24 hours of starting lenalidomide and must either commit to continued abstinence from heterosexual intercourse or begin TWO acceptable methods of birth control; one highly effective and one additional effective method AT THE SAME TIME at least 28 days before starting taking lenalidomide.
7. FCBP must also agree to ongoing pregnancy testing weekly for the first four weeks and then every 28 days while on therapy and at discontinuation of treatment.
8. Men must agree to use a latex condom during sexual contact with a FCBP even if they have had a successful vasectomy. All patients must be counseled at a minimum of every 28 days about pregnancy precautions and risks of fetal exposure.
9. Age 18 and older.
10. Signed, written IRB-approved informed consent.

Exclusion Criteria:

1. Known sensitivity to lenalidomide or thalidomide or it's derivatives
2. Known positivity for HIV or active hepatitis B or C.
3. Pregnant or breast feeding females. Lactating females must agree not to breast feed while taking lenalidomide.
4. History of tuberculosis within the last five years or recent exposure to tuberculosis equal to or less than 6 months.
5. Any serious medical condition, laboratory abnormality, or psychiatric illness that would prevent the subject from signing the informed consent form.
6. 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.
7. Use of any other experimental drug or therapy within 28 days of baseline.
8. Concurrent use of other anti-cancer agents or treatments