Inclusion Criteria:

1. Age >/=15 years.
2. Written informed consent.
3. Patients with chronic lymphoid malignancies that are either refractory to frontline therapy or have relapsed and that have a predicted probability of response of less than 20% with conventional therapy or allogeneic/autologous stem cell transplantation.
4. The following histologies are included: B-cell CLL, B-cell PLL, CLL/PLL, hairy cell leukemia and hairy cell variant, mantle cell leukemia/lymphoma, marginal zone lymphoma/leukemia, splenic lymphoma with villous lymphocytes, CLL with evidence of transformation (e.g., Richter's transformation), large granular lymphocytic leukemia (LGL and NK-cell type).
5. Patients with above mentioned histologies whose malignant cell population have expressed both CD52 and CD20 in >/= 20% of cells as assessed by flow cytometry or immunohistochemistry. Expression of CD20 or CD52 < 20% is permitted if patients received rituximab or alemtuzumab, respectively, within 3 months prior to study start.

Exclusion Criteria:

1. Patients who have previously received Rituximab and CAMPATH-1H in combination are excluded.
2. ECOG performance status of </= 2. (Appendix A)
3. Serum creatinine </= 2mg/dL and total bilirubin of £ 2 mg/dL unless due to direct infiltration of the liver or kidney with malignant cells.
4. Patients with a past history of anaphylaxis following exposure to rat or mouse derived CDR-grafted humanized monoclonal antibodies are excluded.
5. Negative pregnancy test (serum or urine) if female and of childbearing potential only (non-childbearing is defined as greater than one year post-menopausal or surgically sterilized).
6. No prior chemotherapy, immunotherapy, or hormonal therapy within 2 weeks prior to study start. Hormonal replacement therapy is permitted. No prior therapy with monoclonal antibodies for at least 4 weeks prior to study start.
7. Patients at high risk of HBV infection and active HBV infection are excluded.