A 19-year-old man with Philadelphia-positive chronic myelogenous leukemia treated with interferon-alpha (IFN-alpha) therapy for 45 months had systemic lupus erythematosus disease features: malar rash, migratory arthralgias, elevated antinuclear antibodies, elevated antinative DNA, hypocomplementemia, lymphopenia, and proteinuria. After discontinuation of the IFN and initiation of corticosteroids, there was gradual recovery of symptoms, a decline in antinative DNA and antinuclear antibodies to normal levels, and a decrease in proteinuria. The potential association between IFN therapy and the development of systemic lupus erythematosus, and the role of IFN in other autoimmune diseases, is discussed.