A 63-year-old woman developed a clinical and pathological picture of polyarteritis nodosa (PAN). Systemic lupus erythematosus (SLE) had been diagnosed 12 years previously, and she had been symptom and therapy-free for a decade. Development of 'primary' systemic vasculitis in SLE patients has rarely been described previously and the significance of this association remains unclear. The possible explanation for this transition from one connective tissue disease to another is discussed.