The diagnostic value of the nasal biopsy in the early diagnosis of Wegener's granulomatosis and its value in prognosis were examined in 11 patients with a clinicopathological diagnosis of the disease. The vascular lesions found included microabscess in the vascular walls in 82%, leukocytoclastic capillaritis in 73%, fibrinoid necrosis of blood vessels in 45%, leukocytoclastic endovasculitis in 27%, and palisading granuloma in vascular wall in 9% of cases. The extravascular lesions included palisading granuloma in all cases, microabscess in 91%, and diffuse granulomatous tissues in 82%. Palisading microgranuloma (82%) was more frequent than palisading macrogranuloma (45%). After therapy, complete remission occurred in 8 patients, but 3 patients died of sepsis, diffuse pulmonary haemorrhage, and cerebral haemorrhage. Comparison of the frequency of each finding in the nasal biopsy specimens between patients who achieved remission and those who died showed that leukocytoclastic vasculitis was found more commonly in fatal cases, and leukocytoclastic endovasculitis was observed only in fatal cases. Palisading granuloma as a vascular or extravascular lesion is the primary and most important finding in a histopathological diagnosis of Wegener's granulomatosis, microabscess in vascular walls is a secondary but the next most important finding, and leukocytoclastic vasculitis heralds dissemination of the disease and poor prognosis. It requires aggressive therapy.