Inclusion Criteria: Patients must have:

• Pathologically confirmed diagnosis of relapsing or refractory non-Hodgkin's lymphoma that has failed conventional therapy.
• Measurable disease (lesions that can be accurately measured by CT scan and a greatest transverse diameter larger or equal to 1 cm or palpable lesions that both diameters larger or equal to 2 cm).
• Life expectancy of at least 12 weeks. - World Health Organization (WHO) performance status (PS) of 0, 1, or 2.
• Adequate marrow and organ function (details are listed in the protocol).
• Female patients with childbearing potential must have a negative serum pregnancy test within 2 weeks prior to enrollment. Male and female patients must agree to use an effective contraceptive method while on study treatment, if appropriate, and for a minimum of 6 months following study therapy.
• Signed, written informed consent.

Exclusion Criteria: Patients must not have:

• Prior autologous bone marrow or stem cell transplant within 6 months of study entry.
• A history of prior allogeneic bone marrow transplant or organ transplant.
• Previously untreated non-Hodgkin's lymphoma.
• Previously treated with CAMPATH.
• Patients with bulky disease, ie any single mass > 7.5cm.
• Prior radiotherapy to the only site of measurable disease.
• Medical condition requiring chronic use of oral, high-dose corticosteroids.
• Autoimmune thrombocytopenia.
• Use of investigational agents within previous 30 days or any anti-cancer therapy within the previous 3 weeks. Patients must have recovered from all acute toxicities of any prior therapy.
• Past history of anaphylaxis following exposure to humanized monoclonal antibodies.
• Active, uncontrolled infection, including human immunodeficiency virus (HIV) positive.
• Active secondary malignancy.
• Active central nervous system (CNS) involvement with NHL.
• Pregnant or lactating women. Male or female patients who do not agree to use effective contraceptive method(s) during the study.
• Any significant concurrent disease or illness that would, in the opinion of the investigator, compromise patient safety or compliance, or interfere with the interpretation of study results.