Three hundred sixty-seven successive patients suffering from chronic maxillary sinusitis (CMS) were thoroughly examined by means of maxillary sinusoscopy, a CT scan of the facial sinuses, and sinusomanometry (SMM). Ninety-eight cases of unilateral CMS, 269 cases of bilateral CMS, and 444 chronic ethmoidal sinusitis (CES) cases were evaluated. According to SMM, the maxillary ostia were divided into two groups: 1. maxillary ostium patency (MOP) group and 2. the maxillary ostium nonpatency (MONP) group. The unilateral and bilateral pathologies were separately analyzed so as to minimize the effects of general or systemic causes on the results. MONP is, in both bilateral and unilateral groups, significantly linked with the presence of ethmoidal sinusitis (P < 10(-6); P = .026), while the correlation between MOP and the ethmoid status does not appear to be significant in either group. Thus, there seems to be a close relationship between CES and maxillary ostial dyspermeability in cases of CMS.