Inclusion Criteria:

- Binet stage A CLL

- 2 or more risk factors:

- Unmutated IgVH locus (≥98% homology to germline sequence)

- CD38 expression (>7%)

- Deletion of chromosome 11q22 (>20% by FISH)

- Deletion of chromosome 17p13 (>10% by FISH)

- Over 18 years old

- Capable to provide written informed consent

- ECOG performance status < 2

- Life expectancy > 2 years

- Must agree to not share lenalidomide with someone else

- Must agree not to donate blood whilst taking the study drug and for one week after
discontinuation of treatment.

- Female subjects of childbearing potential and all male subjects must agree to comply
with the stipulations of the pregnancy prevention plan.

Exclusion Criteria:

- Current or recent (within the last 1 month) participation in another clinical trial
investigating the action of an investigational medicinal product for the treatment of
CLL

- Pregnant or lactating

- Known positivity for human immunodeficiency virus (HIV) types 1 or 2

- Prior history of malignancies, other than CLL, unless the subject was treated with
curative intent and has been free of the disease for ≥3 years. Exceptions include the
following:

- Basal cell carcinoma of the skin

- Squamous cell carcinoma of the skin

- Carcinoma in situ of the cervix

- Carcinoma in situ of the breast

- Significantly abnormal renal or hepatic function (creatinine clearance < 60ml/min,
serum aspartate aminotransferase (AST) > 3 x upper limit of normal (ULN), serum
bilirubin > 34μmol/l)

- Laboratory tumour lysis syndrome according to the Cairo-Bishop classification.
Subjects may be enrolled when these abnormalities have been corrected.

- Peripheral neuropathy (grade ≥ 2)

- Previous treatment for CLL

- Previous treatment with Thalidomide or immunomodulatory derivative drugs (including
Lenalidomide)

- Treatment with corticosteroids (for CLL or other indications) < 28 days from study
entry

- Evidence of Richter's transformation

- Unsupported absolute neutrophil count < 1x109/l or platelet count < 50x10*9/l not due
to CLL

- Active autoimmune haemolytic anaemia or thrombocytopenia

- Any other medical or psychological condition that in the view of the investigator
would be likely to impact compliance with the protocol or interfere with trial
treatment.