Background: Coexistence of bronchial asthma and allergic nasal polyposis make both disorders more difficult to control with more exacerbation and more eosinophilic inflammation. Aim: to assess the coexistence of subclinical bronchial asthma in patients with allergic nasal polyp refractory to medical therapy and to identify those at risk of developing asthma. Subjects and methods: A case-control study was conducted on 60 allergic nasal polyp patients and 60 healthy subjects. All of them were assessed by peripheral eosinophils%, allergic rhinitis score (SFAR), NOSE-score, endoscopic-sinus examination, sinus computed tomography using Lund and Mackey scoring-system, asthma screening questionnaire (ASQ), spirometric-indices, and histopathological examination of endoscopically  removed polyps. Results: Patients with allergic nasal polyps had significantly lower spirometric-indices than controls. Subclinical asthma was significantly common in patient group than controls (61.7% vs. 10%), it was of mild and moderate severity (83.8% and 16.2%). Allergic nasal polyp patients with coexistence of asthma had significantly higher peripheral eosinophils %, SFAR-score, NOSE-score, Lund and Mackey CT-score, and ASQ score (10, 39.7, 40.5, 40, and 40.1) than patients without asthma (15.2, 15.7, 15.2 and14.1). Moreover, they had significantly common eosinophilic-predominate pathological subtypes (81.1%).