Ultrasound as a diagnostic aid in the evaluation of the sinuses has been a controversial issue. Sensitivities have been reported from 29% to 100% and specificities from 55% to 99%. These wide variations in results from previous studies may have resulted from technical differences. However, the "gold standard" most often used for comparison has been a Water's view radiograph, which has been shown to correlate poorly with intraoperative and CT scan findings. To our knowledge, no one in the English language literature has evaluated sonography of the sinuses with computed tomography as the gold standard. In addition, evaluation of the ethmoid sinus has been neglected by previous studies that have primarily assessed the maxillary sinus. We report the results of a blinded, prospective trial comprised of 41 patients examined by B-mode ultrasound with comparison to computed tomography. Frontal and maxillary sinuses were examined with traditional sonographic techniques and the ethmoid sinuses were scanned with a transglobe technique not previously evaluated in the English language literature. Excluding isolated mucous retention cysts and focal minimal mucosal thickening (defined as < 4 mm), sensitivities for ultrasound of the maxillary, frontal, and ethmoid sinuses were 100% each. Specificities were 98% for the maxillary sinus, 100% for the frontal sinus, and 94% for the ethmoid sinus. Technical aspects and implications of this and previous reports will be discussed.