Inclusion Criteria:

- Histologically confirmed B-cell non-Hodgkin's lymphoma OR acute lymphoblastic
leukemia

- CD20+ (confirmed by flow cytometry of tumor tissue, involved marrow, or CD20
immunostaining)

- The following histologies are generally CD20+ and are eligible:

- Diffuse large B-cell lymphoma, mediastinal (thymic) large B-cell lymphoma,
or follicular lymphoma, grade III (rare), documented by flow cytometry or
appropriate immunohistochemistry, any stage

- Burkitt's lymphoma or atypical Burkitt's/Burkitt-like lymphoma, any stage

- B-cell acute lymphoblastic leukemia, with FABL3 morphology and/or
demonstration of surface immunoglobin by flow cytometry

- Atypical precursor B-cell lymphoblastic lymphoma or other unusual
histologies that are CD20+

- Measurable disease by clinical, radiographic, or histologic criteria

- Must be in first or later recurrence or have disease that is primarily refractory to
conventional therapy

- No isolated CNS disease

- Performance status - ECOG 0-2

- At least 2 months

- Absolute neutrophil count ≥ 1,000/mm^3*

- Platelet count ≥ 100,000/mm^3 (transfusion independent)*

- Hemoglobin ≥ 10.0 g/dL (RBC transfusion allowed)*

- Bilirubin ≤ 1.5 times normal

- ALT < 2.5 times normal

- No chronic renal insufficiency

- Renal insufficiency allowed provided it is secondary to tumor lysis syndrome

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception during and for 3 months after study
treatment

- HIV negative

- No active uncontrolled infection

- Seizure disorder allowed if well controlled with anticonvulsants

- No CNS toxicity greater than grade II

- At least 24 hours since prior growth factor(s)

- At least 60 days since prior biologic (antineoplastic) therapy

- Prior stem cell transplantation allowed provided the following criteria are met:

- More than 60 days since transplantation

- Hematopoietic lab value requirements are met (See Hematopoietic)

- No evidence of graft-versus-host disease (if post-allogeneic transplantation)

- Prior monoclonal antibody therapy allowed (including rituximab)

- No other concurrent immunomodulating agents

- More than 2 weeks since prior myelosuppressive chemotherapy (4 weeks for
nitrosoureas)

- No other concurrent chemotherapy

- No concurrent steroids (except for rituximab infusion-related symptoms)

- At least 2 weeks since prior local palliative radiotherapy (small port)

- At least 6 weeks since prior substantial bone marrow radiotherapy

- At least 6 months since prior craniospinal radiotherapy or radiotherapy to 50% or
more of the pelvis

- Concurrent radiotherapy to localized painful, airway-compromising, or other acute
organ-threatening lesions allowed provided at least 1 measurable lesion is not
irradiated

- Recovered from prior therapy

- No concurrent participation in another phase II study