Inclusion Criteria:

• Age >= 18 years (CLL does not occur in the pediatric population).
• Signed informed consent.
• World Health Organization (WHO) performance status of 0, 1, or 2.
• Patients with B-CLL who have received fludarabine and are either refractory to frontline therapy or have relapsed within six months from receiving fludarabine-based therapy. Patients previously treated with Campath-1H are eligible.
• Serum creatinine <= 2mg/dL, total bilirubin <= 2mg/dL, and SGPT <= 3x upper limit of normal (ULN) unless due to direct infiltration of the liver or kidney with malignant cells.

Exclusion Criteria:

• Past history of anaphylaxis, following exposure to rat or mouse derived CDR-grafted humanized monoclonal antibodies.
• Prior chemotherapy, immunotherapy, or hormonal therapy within 2 weeks prior to study start. Hormonal replacement therapy is permitted. Prior therapy with monoclonal antibodies for at least 4 weeks prior to study start.
• Pregnant or nursing women or any patient of childbearing age unwilling to practice an acceptable form of contraception.
• Patients with history of HIV positivity.
• Active secondary malignancy.
• Active uncontrolled infection or any major systemic or other illness that would, in the opinion of the investigator, interfere with the patient’s ability to comply with the protocol, compromise patient safety or interfere with the interpretation of study results.