In this multicenter trial, we will investigate the use of fludarabine plus rituximab, followed by Campath-1H, in previously untreated patients with CLL/SLL. Patients who are elderly, or who are considered unlikely to tolerate this combination therapy well, will receive single agent rituximab followed by Campath-1H.

Upon determination of eligibility, all patients will receive:

Fludarabine + Rituximab + CAMPATH-1H

Patients who are judged by the investigator not to be candidates for fludarabine due to advanced age, marginal performance status or coexistent medical conditions will receive rituximab alone followed by CAMPATH-1H.

Inclusion Criteria:

To be included in this study, you must meet the following criteria:

• Histologically proven B-cell CLL/SLL
• Positive staining for CD20 antigen
• No systemic chemotherapy.
• Measurable or evaluable disease
• Able to perform activities of daily living with minimal assistance
• Age > 18 years
• Life expectancy > 12 weeks
• Adequate liver and kidney function
• Must be accessible for treatment and follow-up
• Must give written informed consent prior to entering this study.

Exclusion Criteria:

You cannot participate in this study if any of the following apply to you:

• Female pregnant or lactating
• Unstabilized active infection on the basis of neutropenia
• History of previous severe opportunistic infections
• Serious underlying medical conditions
• Central nervous system involvement
• History of other neoplasms, either active or treated within five years

Please note: There are additional inclusion/exclusion criteria. The study center will determine if you meet all of the criteria. If you do not qualify for the trial, study personnel will explain the reasons. If you do qualify, study personnel will explain the trial in detail and answer any questions you may have.