We have studied seventy-five patients with recurrent urticaria and angio-oedema of more than 4 months duration and with positive provocation tests to aspirin, azo dyes, and/or benzoates. Cross-reactions between the test compounds were common. The patients were recommended to be on a diet free from salicylates, benzoates, and azo dyes. They were then followed for 6-24 months. At the follow-up, 24% were free from symptoms, 57% considered themselves much better and 19% stated that they were slightly better or unchanged. All patients had followed the diet for at least 1-3 months. Most of those who became totally free of symptoms did not continue with the diet, while most of the patients who considered themselves much better found that it was necessary to continue on the recommended diet. They usually developed symptoms as soon as they ingested something containing azo dyes or benzoates. To be able to maintain such a diet, it is important that the content of additives in food and drugs be properly declared.