Causes and precipitating factors for systemic necrotizing angiitis (NA) with asthma were sought in 43 patients, focusing on a history of vaccination and desensitization. Mean age of patients was 43.2 years. Diagnosis was based on histopathologic findings in 25 patients, arteriography in 2, and clinical criteria in 16. History of allergic manifestations (asthma, rhinitis, eczema, urticaria) was present in the family of 19 patients. Forty-two patients presented with asthma before development of NA and 23 of them were treated with steroids. Nineteen subjects gave a history of desensitization and 5 of vaccination in the 4 weeks preceding the disease. The main symptoms of NA were asthma in 43, fever in 25, weight loss in 31, peripheral neuropathy in 29, cutaneous signs in 25, digestive signs in 16 (abdominal pain, digestive bleeding, bowel perforation), noninfectious pneumopathy with pulmonary infiltrates in 33. Eosinophilia was 8,212 +/- 6,214/mm3. Antigen HBs was found in 2 of 30 patients. Prognosis of NA with asthma was good in 15 patients who recovered completely from the disease. Seven patients died and the other patients improved but remained under treatment. The survival curve showed that 75% of patients were alive after 60 months. Our findings suggest that different causes can be considered responsible for NA, and that, in cases of NA with asthma, there is reason to consider vaccination and desensitization as precipitating factors.