Inclusion Criteria:

• 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.
• 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.
• ECOG/WHO status of 0-2.
• Adequate renal and hepatic function (creatinine equal to or less than 2mg/dL - total bilirubin equal to or less than 2).
• 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).
• 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.
• 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.
• 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.
• Age 18 and older.
• Signed, written IRB-approved informed consent.

Exclusion Criteria:

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