OBJECTIVES: I. Determine the effects of adjuvant low-dose extended-duration interferon alfa on disease-free and overall survival in patients with completely resected malignant melanoma at high risk of recurrence. II. Determine any correlation between patient age or sex and the effects of interferon therapy on disease-free and overall survival. III. Describe the toxic effects of this treatment. IV. Evaluate the economic implications of implementing effective interferon therapy in these patients.