Wegener's granulomatosis (WG) frequently involves the upper respiratory tract, and nasal mucosal biopsy is often initially used to establish the diagnosis. To evaluate the diagnostic efficacy of nasal biopsy in WG, we reviewed the pathologic features of 30 such biopsy specimens from 17 patients with well-documented WG. Active vasculitis (granulomatous or nongranulomatous) was identified in seven of the patients (41%). The presence of extravascular foci of necrosis in lung biopsy samples has recently received attention as a characteristic feature of WG. Similar foci were found in the nasal samples from six of our patients, although vasculitis was absent in the samples from two of them. If extravascular foci of necrosis are regarded as characteristic or even diagnostic of WG, two additional patients in our series could be regarded as having had diagnostic nasal biopsies (nine of 17 patients). Nasal biopsy could thus be considered as diagnostic in 53% of the patients. Samples larger than 5 mm in greatest dimension were more likely to contain diagnostic features than were smaller samples (P = 0.002).