OBJECTIVES: I. Determine the response in patients with minimally treated or previously untreated advanced low-grade non-Hodgkin's lymphoma treated with pegylated interferon alfa-2b. II. Determine the effects of this treatment regimen on the immune system by measuring T-cell subsets and NK cells in this patient population. III. Determine event-free and progression-free survival in this patient population treated with this regimen. IV. Evaluate the toxicity profile of this treatment regimen in these patients.