The aim of this study was to investigate the frequency of sinusitis in patients with pneumonia. Among 50 Consecutive patients with pneumonia, 19 cases, which had Waters' roentgenograms in their Cites. were retrospectively reviewed in relation with sinusitis. Sixteen of them had sinusitis signs in their roentgenograms. The sinusitis frequency was 84% in patients with pneumonia who had paranasal sinus roentgenograms. These findings suggest that sinusitis may be an important causative factor for pneumonia and that it Should be considered when evaluating a patient with pneumonia. (C) 2002 Elsevier Science Inc. All rights reserved.