By a careful ENT and oral examination of 111 patients with suspected chronic maxillary sinusitis, the diagnosis was verified in only 56% (62/111). In 29 of these 62 patients (47%) a relation to dental infections was found, periodontitis being as frequent as apical granulomas. In 61% of the patients, in whom the diagnosis chronic maxillary sinusitis could not be verified, dental infections and/or myofascial pain dysfunction syndrome (MPD) were the most common and likely cause of the symptoms. A careful oral examination including dental radiographs is thus important in patients with chronic maxillary sinusitis.