RATIONALE: Monoclonal antibodies such as rituximab can locate cancer cells and either kill them or deliver cancer-killing substances to them without harming normal cells. Drugs used in chemotherapy use different ways to stop cancer cells from dividing so they stop growing or die. Combining more than one chemotherapy drug with rituximab may kill more cancer cells.

PURPOSE: Phase II trial to study the effectiveness of rituximab plus combination chemotherapy in treating patients who have intermediate-grade or high-grade non-Hodgkin's lymphoma.

OBJECTIVES: I. Determine the rate of complete response and partial response in patients with intermediate or high grade non-Hodgkin's lymphoma treated with rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP). II. Determine the toxicity of this regimen in these patients. III. Determine the disease-free and overall survival, time to response, and time to disease progression in patients treated with this regimen.

OUTLINE: This is a multicenter study. Patients are stratified according to the number of risk factors (0-2 vs 3-5). Risk factors include age (no greater than 60 vs greater than 60), tumor stage (II vs III or IV), number of extranodal sites (no more than 1 vs more than 1), performance status (0-1 vs 2-4), and serum LDH level (no greater than normal vs greater than normal). Patients receive rituximab IV on day 1; cyclophosphamide, doxorubicin, and vincristine IV on day 3; and oral prednisone on days 3-7. Patients over 60 also receive filgrastim (G-CSF) subcutaneously beginning on day 4 and continuing until blood counts recover (all other patients receive G-CSF as secondary prophylaxis). Treatment continues every 3 weeks for 4 courses in the absence of disease progression or unacceptable toxicity. Patients who respond receive 2 more courses. Patients who have no measurable disease after 6 courses receive rituximab IV once weekly for 4 consecutive weeks. This treatment continues every 6 months for 4 courses in the absence of disease progression or unacceptable toxicity. Patients who have measurable disease after 6 courses of chemotherapy receive 2 more courses for a maximum of 8 courses of CHOP, followed by maintenance therapy with rituximab (as described above). Patients are followed every 6 months for 2 years.

PROJECTED ACCRUAL: Approximately 100 patients will be accrued for this study.

DISEASE CHARACTERISTICS: Histologically confirmed intermediate or high grade non-Hodgkin's lymphoma Stage II, III, or IV disease B-cell where lymphoid cells are CD20 or CD19 positive No mantle cell, lymphoblastic, or peripheral T-cell non-Hodgkin's lymphoma Measurable or evaluable disease No prior treatment for lymphoma No known CNS metastases A new classification scheme for adult non-Hodgkin's lymphoma has been adopted by PDQ. The terminology of "indolent" or "aggressive" lymphoma will replace the former terminology of "low", "intermediate", or "high" grade lymphoma. However, this protocol uses the former terminology.

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 60-100% Life expectancy: At least 12 weeks Hematopoietic: Unless documented bone marrow disease: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: SGOT and SGPT no greater than 3 times upper limit of normal Bilirubin no greater than 1.5 mg/dL Renal: Creatinine no greater than 2.0 mg/dL Cardiovascular: No history of severe heart disease, cardiomyopathy, or congestive heart failure LVEF normal by MUGA or echocardiogram Other: Not pregnant or nursing Fertile patients must use effective contraception No active infection as defined by: Clinical syndrome consistent with a viral or bacterial infection (e.g., influenza, upper respiratory infection, urinary tract infection) OR Fever with a clinical site of infection identified OR Microbiologically documented infection, including, but not limited to, bacteremia or septicemia No known HIV positivity No known sensitivity to E. coli derivatives (e.g., asparaginase, human insulin, human growth hormone, interferon alfa-2b) No other prior malignancy within the past 5 years except surgically cured basal or squamous cell skin cancer or carcinoma in situ of the cervix No psychiatric, addictive, or other disorder that may preclude study

PRIOR CONCURRENT THERAPY: Biologic therapy: See Disease Characteristics No concurrent biologic therapy except epoetin alfa No white blood cell transfusions Chemotherapy: See Disease Characteristics No concurrent chemotherapy Endocrine therapy: Not specified Radiotherapy: See Disease Characteristics No concurrent radiotherapy Surgery: At least 2 weeks since prior major surgery Other: No other concurrent investigational therapy No prophylactic antibiotics