Low risk protocol: Patients with small non-cleaved (Burkitt or Burkitt-like) or diffuse large cell lymphomas with a) minimal extra-abdominal disease as the sole site of disease and a serum LDH less than 1.5 times the upper limit of normal (NIH patients, less than 350 U/L) or b) completely resected small, localized abdominal mass (involved segmental lymph nodes permitted for gastrointestinal disease) and a serum LDH level less than 1.5 times the upper limit of normal (NIH patients, less than 350 U/L).