Three cases of necrotizing granulomatous vasculitis of the Wegener's type involving the breast are described. In each, the presumed diagnosis was localized or metastatic carcinoma. The breast lesion and other manifestations of Wegener's granulomatosis developed concomitantly in one patient, and the breast lesion appeared several months before classic pulmonary symptoms in another. In the third patient, not only were her upper and lower airway symptoms explained only in retrospect, but even the significance of the breast biopsy findings was clarified only after other aspects of Wegener's granulomatosis developed. All patients ultimately demonstrated a good response to corticosteroids and cyclophosphamide therapy. Wegener's granulomatosis is a rare lesion affecting the breast but should nonetheless be considered in the evaluation of any breast mass.