OBJECTIVES: I. Determine the efficacy and response rate of triple antibiotic therapy for Helicobacter pylori in the healing of lesions in patients with low grade gastric lymphoma. II. Assess the efficacy of chlorambucil in the prevention of relapse in patients after complete eradication of low grade gastric lymphoma. III. Determine the natural history of unresected or partially resected low grade gastric lymphoma treated medically.