We describe a patient with X-linked chronic granulomatous disease (CGD) who developed systemic lupus erythematosus, which was characterized by photosensitivity, malar rash, glomerulonephritis, leukopenia, hypocomplementemia, antinuclear antibodies, and anti-double-stranded DNA antibodies, at age 3. The patient's mother is an asymptomatic carrier of CGD, and her other son (the patient's half-brother) also has CGD. Neither the mother nor the brother has clinical or serologic evidence of systemic lupus erythematosus. Previous cases of discoid lupus-like skin lesions have been reported both in carriers and in patients with CGD. Our patient represents the first reported case of an individual with convincing clinical, serologic, and pathologic evidence of systemic lupus erythematosus. The association between defective host defense mechanisms and autoimmune phenomena has been described previously in patients with Job's syndrome and in patients with B cell and T cell deficiency disorders, including the acquired immunodeficiency syndrome. The relationship between the known leukocyte defects in CGD and the pathogenesis of a lupus-like illness is unclear.