A homogeneous group of 30 patients who were operated over a 5-year period for odontogenic sinusitis using a buccosinusal communication following Caldwell-Luc's technique were studied. A marked discrepancy between the conventional X-ray picture and the clinical picture emerged from these 30 case studies. So as to find an explanation for this discrepancy, all patients underwent CAT tests. On the basis of a critical evaluation of the results obtained it is suggested that patients be followed using a postoperative instrumental control protocol.