Background: Chronic urticaria and concurrent angioedema are frustrating problems for both physicians and patients. Methods: 100 patients with chronic urticaria (mean duration 33.3+/-48.2 months) attending the urticaria consulting hour of our Department of Dermatology within I year were carefully analyzed for pathogenesis to avoid extensive unnecessary diagnostic approach in the future, Results: In 43 cases a potential infectious trigger could be identified, 35 were of idiopathic origin, and 15 demonstrated pseudoallergic reactions to acetylsalicylic acid or food additives, 5 had antibodies to thyroid gland, and 2 had malignant diseases. Of patients with foci. 26 had Helicobacter pylori-associated gastritis, 9 chronic tonsillitis or sinusitis, 4 infections with Epstein-Barr virus or cytomegalovirus, 2 dental focal infections and 2 suffered from Yersinia infection. Hi,oh prevalence of H. pylori gastritis was found since 47% of patients showed elevated H, pylori-specific IgA and/or IgG antibodies. 27 patients underwent endoscopy and in all but 1 (96%) antral H. pylori infection was found. In contrast, a prevalence rate of 37% among asymptomatic adults has been published. Disappearance (67%) or improvement of urticaria (24%) occurred in most antimicrobially treated patients after 3-12 weeks. In contrast, only 50% of untreated H. pylori-seropositive patients with chronic urticaria showed spontaneous remission or improvement within 12 weeks. Prevalence of H. pylori infection may even be underestimated since only 27/100 patients underwent endoscopy. It is suggested that H. pylori Infection may be present at least in all seropositive subjects (47%). Moreover,we found H. pylori infection in 2 seronegative subjects demonstrating gastric complaints. Conclusions: Thus, measurement of H. pylori-specific antibodies and/or gastroscopy should be included in the diagnostic management of chronic urticaria to identify patients who may profit from eradication treatment with disappearance of long-standing and annoying urticaria symptomatology.