The purpose of this study is to assess the safety, tolerance, and immunologic effects of interleukin-10 (IL-10), in patients with Wegener's granulomatosis. A secondary objective is to determine if IL-10 demonstrates sufficient anti-inflammatory activity in the treatment of Wegener's granulomatosis to warrant further study in a larger trial. In this study, IL-10 will be given either alone or in combination with standard therapeutic agents, usually consisting of cyclophosphamide, methotrexate, and/or prednisone. Patients will be eligible to receive IL-10 when there is evidence of active disease. IL-10 will be administered by subcutaneous injection at a dose of 4 µ (Micro)g/kg/day for 28 days.