Aim: To evaluate the prevalence of paranasal sinus pathology and investigate the relationship of sinusoidal mucosal inflammation with serum eosinophilia and IgE levels in asthmatic outpatients. Methods: Following the medical history and physical examination, we evaluated sinus x-rays (Water's graphy) in 82 asthmatic outpatients. Pulmonary function tests were performed with a dry spirometer. Serum eosinophil percentage was determined using a hemocounter and serum total IgE level by nephelometric technique. Statistical analyses were done by X-square, t-test and correlation tests. Results: The mean age of patients was 42.82±13.28 years and 74% were women. Duration of asthma was 7.50±7.36 years. 82% of patients were symptomatic for asthma during evaluation. Mean FEV1 was 1.98±0.69L and FEV1/FVC was 66±14%. Serum total IgE level was 137.85±147.53 IU/ml while eosinophil percentage was found to be 4.05±3.72. Water's graphy was normal in 44 of the patients (53.6%). At least one of radiological findings of sinusitis was detected in 38 of the cases (46.4%). There was maxillary sinus mucosal thickening in 35.4%, air-fluid level in 14.6% and polyp-cyst in 6.1%.There was no correlation between paranasal sinus pathology and duration of asthma (p=0.065) or severity of asthma (FEV1%) (p=0.856). There was no difference in eosinophil levels between asthmatic patients who had a paranasal sinus pathology and the ones who did not (p=0.832). Although mean serum IgE level was higher in patients with sinusitis, statistically significant difference was not detected (p=0.968). Discussion: Proper management of sinusitis may improve asthmatic symptoms and decrease need for medication. We suggest that asthmatic patients should be searched routinely for the presence of occult sinusitis.