Inclusion Criteria:

1. Age 18-75 years at the time of signing the informed consent form.
2. Disease: CLL in relapse, after failing conventional chemo-antibody combination therapy; CLL patients who failed to achieve CR with frontline conventional chemo-antibody; CLL patients with 17p deletion; CLL in Richter's.
3. Able to adhere to the study visit schedule and other protocol requirements.
4. Donor: HLA compatible related (HLA-A,-B,-DRBI matched or with one-antigen mismatched) or HLA compatible unrelated.
5. ECOG performance status of </= 2 at study entry
6. FEV1, FVC and DLCO >/= 40%.
7. Left ventricular EF > 40% with no uncontrolled arrhythmias or symptomatic heart disease.
8. Serum creatinine </= 1.6 mg/dL. Serum bilirubin < 1.6 mg/dL.
9. SGPT < 2x upper limit of normal.
10. Voluntary signed, written IRB-approved informed consent before performance of any study-related procedure not part of normal medical care, with the understanding that consent may be withdrawn by the subject at any time without prejudice to future medical care.
11. All previous cancer therapy, including radiation, hormonal therapy and surgery, must have been discontinued at least 3 weeks prior to treatment in this study.
12. Disease free of prior malignancies for >/= 5 years with exception of currently treated basal cell, squamous cell carcinoma of the skin, or carcinoma "insitu" of the cervix or breast.
13. Females of childbearing potential (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 study entry.
14. Disease must be chemosensitive (ie, patients must have PR or better based on CT Scans, PET Scan, and bone marrow biopsy).
15. Patients suspected to have Richter's transformation (such as elevated LDH) and/or who are PET positive, should have a lymph node biopsy to assess histological status of the disease
16. Patients must be off of alemtuzumab for 6 weeks prior to consenting.

Exclusion Criteria:

1. Any serious medical condition, laboratory abnormality, or psychiatric illness that would prevent the subject from signing the informed consent form.
2. Pregnant or breast feeding females. (Lactating females must agree not to breast feed while taking lenalidomide).
3. 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.
4. Use of any other experimental drug or therapy within 28 days of baseline.
5. Known hypersensitivity to thalidomide, lenalidomide, bendamustine, fludarabine. For patients will unrelated donors: Known hypersensitivity to thymoglobulin.
6. The development of erythema nodosum if characterized by a desquamating rash while taking thalidomide or similar drugs.
7. Concurrent use of other anti-cancer agents or treatments.
8. Known positive for HIV or infectious hepatitis, type A, B or C.
9. Sinuses should be evaluated by either CT neck or CT sinuses to exclude infections
10. Deep-vein thrombosis or pulmonary embolism within 3 months of study entry.
11. History of serious infection requiring hospitalization within the last 3 months of consenting.