Inclusion Criteria:

1. Histologically or cytologically proven, stage III or IV, low-grade B-cell NHL, as
defined by the updated WHO modification of the REAL classification for peripheral
B-cell neoplasms: B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma;
Lymphoplasmacytic lymphoma/immunocytoma; Follicular lymphoma; Extranodal marginal
zone B-cell lymphoma of MALT type; Nodal marginal zone B-cell lymphoma (+/-
monocytoid B-cells); Lymphoma with primarily bone marrow-only disease are considered
eligible

2. Bulky lymphoma or Stage II disease requiring chemotherapy will be considered for
enrollment with documented Sponsor Investigator approval prior to registration.

3. CT or MRI scans confirming measurable tumor size (lymph node must be >1cm in its
longest transverse diameter). Measurement by physical exam is acceptable in the case
of palpable and reproducibly measurable axillary or other superficial tumors.

4. Positive expression of CD20 by biopsy or circulating lymphocytes.

5. Zero or one prior chemotherapeutic or immunotherapeutic treatment regimen for B-cell
NHL.

6. Male or female greater than or equal to 18 years of age.

7. ECOG performance status of 0-2.

8. Adequate renal function: Creatinine less than 1.5 mg/dL; BUN less than 30 mg/dL or a
creatinine clearance greater than or equal to 60 mL/min based on calculation of
creatinine clearance using the Cockcroft-Gault method or from a 24-hour urine
collection. Creatinine clearance 40- 59 mL/min from a 24-hour urine collection would
require a Nipent dose reduction of 25%. Patients with a Creatinine clearance <40
mL/min from a 24-hour urine collection will be excluded.

9. Adequate bone marrow function: ANC greater than or equal to 1,000 cells/µL; Platelet
count greater than or equal to 75,000 cells/µL; Hemoglobin greater than or equal to 9
g/dL. Patients with idiopathic thrombocytopenia or autoimmune hemolytic anemia are
eligible with prior approval of Sponsor Investigator.

10. Adequate liver function: Bilirubin less than or equal to 2.0 mg/dL; AST and ALT less
than or equal to 5 times ULN.

11. Adequate cardiac function in the judgment of the Investigator, including NYHA
classification of I or II.

12. Female patients of childbearing potential must have a negative serum pregnancy test
within 7 days prior to registration.

13. Patient agrees to use an acceptable method of birth control, if fertile patient (male
or female), to avoid pregnancy for the duration of the study and for at least 3
months thereafter.

14. Completed Patient Informed Consent Form.

Exclusion Criteria:

1. Previous or current intermediate or high-grade lymphoma.

2. WBC greater than 30,000 cells/µL.

3. Received prior therapy using Rituxan, unless such therapy was completed at least 6
months prior to study registration. Patients whose disease was non-responsive to
prior Rituxan therapy will be excluded.

4. Known sensitivity to Nipent, Rituxan, Cytoxan or any component of these drugs.

5. Patient received replacement steroid therapy less than 4 weeks prior to study
registration.

6. History of other malignancy that could affect the diagnosis or assessment of the
study treatment.

7. Known human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS)
illness.

8. Known prior history of and/or active viral hepatitis (HBV or HCV).

9. Patient is unable to comply with the requirements of this study.

10. Patients with Richter's transformation will be excluded.