Background: Patients with allergic rhinitis (AR) and perennial allergen sensitization are at increased risk for asthma. Objectives: To determine the allergic profile of patients with clinical AR in regions of the coastal Mediterranean compared with the inland southern desert area of Israel and the impact of specific allergen sensitization on the prevalence of asthma in these patients. Methods: Retrospective evaluation of medical records from patients referred for evaluation during 2002 and 2003 to the allergy clinics of 3 medical centers located in different geoclimatic areas. Results: A total of 479 patients with AR were included (64% from the humid Mediterranean coast and 36% from the arid desert area), with a mean age of 32.8 years (range, 6-84 years). Sixty percent of the patients were male, and 33% had an additional diagnosis of asthma. Mite sensitization was 84%; cockroach, 34%; trees, 43%; weeds, 40%; grasses, 53%; and fungi, 30%. There were no significant differences in the prevalence of sensitization to any of the evaluated allergens except for weeds, which was higher in the arid region. A diagnosis of asthma was significantly associated with mite sensitization in the Mediterranean area (odds ratio, 2.24; 95% confidence interval, 1.14-4.4; P = .02) and mold sensitization in the arid climate zone (odds ratio, 2.18; 95% confidence interval, 1.05-4.6; P = .04). Conclusion: Although sensitization to mites is high in the coastal areas and in the Negev desert-like environment, the presence of asthma in patients with AR is associated with mite sensitization in the humid environment but with fungal sensitization in the more arid environment.