Many different methods have been described to obtain sinus culture from patients with chronic sinusitis. However, these methods presented limited information how they had prevented from the contamination with nasal flora. The purpose of this study is to demonstrate and describe a contamination-free technique to obtain culture from involved sinus during endoscopic sinus surgery (ESS). We prepared a cotton-tipped contamination-free swab. This applicator was inserted inside the sinus through ostium or inside the cavity directly established during ESS, and the swab was introduced directly into the implicated area. Thirty-five adult patients with chronic sinusitis who underwent ESS participated in the study. During ESS, the number of cultivated pathogenic microorganisms of the cultures obtained by our method was statistically significantly higher than the cultures obtained by the classic nasal cavity cultures (P = .0296). However, the number of cultivated bacteria (coagulase-negative Staphylococcus, alpha-hemolytic Streptococcus, and Corynebacterium spp.) after the contamination was lower than those of nasal cavity culture (P =.0296). During ESS, the identification of the pathogen in sinusitis with endoscopically guided narrow-bore sinus culture applicator is a reliable diagnostic method compared with the classic culture techniques. (c) 2007 Elsevier Inc. All rights reserved.