OUTLINE: Patients are assigned to Regimens A, B, and C according to histology and extent of disease and the degree of immunosuppression as follows: Regimen A: Patients with Ann Arbor stage I intermediate grade or immunoblastic lymphoma with measurable nonbulky disease (less than 7 cm), low LDH (less than 686), and no prior opportunistic infection irrespective of T4 count; also those with nonmeasurable stage I extranodal primaries (infiltration of less than 2/3 of an organ site, e.g., stomach, rectum, esophagus, sinus cavity) irrespective of T4 count. Regimen B: All patients (except primary brain lymphoma patients) not assigned to Regimen A who have T4 counts of at least 200 and no history of opportunistic infection; includes all stages of small noncleaved cell lymphoma and bulky stage I and stages II-IV intermediate grade and immunoblastic lymphoma. Regimen C: Patients not assigned to Regimen A or B, i.e., those with T4 counts less than 200 and/or a history of opportunistic infection and those with primary brain lymphoma. The following acronyms are used: ARA-C Cytarabine, NSC-63878 BLEO Bleomycin, NSC-125066 CDDP Cisplatin, NSC-119875 CF Leucovorin calcium, NSC-3590 CTX Cyclophosphamide, NSC-26271 DOX Doxorubicin, NSC-123127 5-FU Fluorouracil, NSC-19893 G-CSF Granulocyte Colony-Stimulating Factor (Amgen), NSC-614629 IFF Ifosfamide, NSC-109723 MePRDL Methylprednisolone succinate Mesna Mercaptoethane sulfonate, NSC-113891 MTX Methotrexate, NSC-740 PRED Prednisone, NSC-10023 VCR Vincristine, NSC-67574 VP-16 Etoposide, NSC-141540 ZDV Zidovudine, NSC-602670 Regimen A: 5-Drug Combination Chemotherapy followed by Radiotherapy. CHOP-BLEO: CTX; DOX; VCR; PRED; BLEO; followed by involved-field irradiation with megavoltage equipment. Regimen B: 4-Drug Combination Chemotherapy alternating with 3-Drug Combination Chemotherapy followed, as indicated, by Radiotherapy. ASHAP: DOX; MePRDL; ARA-C; CDDP; alternating with IMVP-16: IFF/Mesna; MTX/CF; VP-16; followed, in selected patients with initially bulky localized disease, by involved-field irradiation with megavoltage equipment. Regimen C: 2-Drug Combination Chemotherapy with Drug Modulation followed, as indicated, by Radiotherapy. FLEP: 5-FU/CF/CDDP; followed, in selected patients with initially bulky localized disease, by involved-field irradiation with megavoltage equipment. Prior to starting chemotherapy, patients with primary brain lymphoma receive a course of cranial irradiation using accelerator beams with photon energies of 6-15 MV.