Inclusion Criteria:

1. Patients must have histologically confirmed newly diagnosed follicular B-cell lymphoma.
2. Patients must have measurable disease, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded) as >/= 20 mm with conventional techniques or as >/= 10 mm with spiral CT scan.
3. Patients should not have received prior therapy of any kind for follicular B-cell lymphoma.
4. Age >/= 18 years. Because no dosing or adverse event data are currently available for the use of rituximab in combination with sargramostim in patients (males or females) <18 years of age, children are excluded from this study.
5. ECOG performance status </= 2 (Karnofsky >/= 60%).
6. Patients must have normal organ and marrow function as defined below: - leukocytes >/= 3,000/microL; - absolute neutrophil count >/= 1,500/microL; - platelets >/= 100,000/microL; -total bilirubin within normal institutional limits; - AST(SGOT)/ALT(SGPT) </= 2.5 X institutional upper limit of normal; - creatinine within normal institutional limits OR - creatinine clearance >/= 60 mL/min/1.73 m^2 for patients with creatinine levels above institutional normal
7. Hemoglobin >/= 8.0 gm/dL
8. The effects of rituximab and sargramostim on the developing human fetus at the recommended therapeutic doses are unknown. For this reason women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately.
9. Ability to understand and the willingness to sign an informed consent document.

Exclusion Criteria:

1. Prior therapy of any kind for follicular B-cell lymphoma.
2. Patients may not be receiving any other investigational agents.
3. Patients with known brain metastases should be excluded from this clinical trial because of their poor prognosis and because they often develop progressive neurologic dysfunction that would confound the evaluation of neurologic and other adverse events.
4. History of allergic reactions attributed to compounds of similar chemical or biologic composition to rituximab or other agents used in the study.
5. Rituximab is contraindicated in patients with known anaphylaxis or IgE-mediated hypersensitivity to murine proteins. Sargramostim is contraindicated in patients with excessive leukemic myeloid blasts, with known hypersensitivity to GM-CSF or yeast-derived components of the recombinant, and for concomitant (or within 24 hours ± of) uses with chemotherapy or radiotherapy.
6. Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.
7. Pregnant women are excluded from this study.
8. Patients with immune deficiency are at increased risk of lethal infections when treated with marrow-suppressive therapy. Therefore, HIV-positive patients receiving combination anti-retroviral therapy are excluded from the study because of possible pharmacokinetic interactions.
9. Patients with evidence of active or prior infection of Hepatitis B are excluded. (Note: Persons vaccinated for Hepatitis B who have positive antibodies are not excluded).