Inclusion Criteria:

- Signed IRB-approved informed consent.

- Greater than 18 years of age

- Proof of CD23+ CLL or small lymphocytic lymphoma (SLL)

- Progressive disease after at least 1 course of chemotherapy

- Acceptable hematologic status, liver function, renal function, and pulmonary function

- Patients of reproductive potential must agree to follow accepted birth control
methods during treatment and for 3 months after completion of treatment

Exclusion Criteria:

- Previous exposure to IDEC-152 or other anti-CD23 antibodies

- Presence of HIV infection or AIDS

- Serious nonmalignant disease

- Active uncontrolled bacterial, viral or fungal infections.

- Clinically active autoimmune disease

- Pregnant or currently breast feeding