The purpose of this study is to determine the safety and effectiveness of combination therapy with Proleukin and Rituxan on patients with intermediate-and high- grade Non-Hodgkin's lymphoma.

Inclusion:

• Diagnosis: CD20+ B-cell non-Hodgkin's lymphoma (NHL) classified as intermediate- or high-grade according to the Working Formulation, subtypes D to H. Must have measureable progressive or refractory disease after no more than three prior chemotherapy regimens.

Exclusion:

• Clinically significant cardiac dysfunction, or a history of myocardial infarction or heart failure within 6 months of first study treatment
• Clinically significant pulmonary dysfunction.
• Liver disease (note hepatitis C seropositive subjects may be enrolled if they have no active disease as demonstrated by undetectable HCV viral loads, biopsy showing no active disease, and/or history of normal transaminases on at least three different dates within one year of first study treatment).
• Symptomatic thyroid disease requiring medical intervention other than replacement treatment for hypothyroidism.
• History of autoimmune disease.
• History of positive serology for human immunodeficiency virus (HIV).