I have often been impressed by the importance placed by medical students and some physicians on transillumination of the paranasal sinuses. The presence or absence of clear transillumination is sometimes regarded as a significant sign, without consideration of other physical findings or the type of skull being transilluminated. Otolaryngologists, in general, regard transillumination as a confirmatory sign of limited value and evaluate it on the basis of the history and the information obtained on anterior and posterior rhinoscopy. A record of a previous examination is advantageous for comparison. The test is regarded as negative if the sinuses transilluminate equally and well; if one or both sinuses show impaired transmissibility of light, the test is regarded as positive. Fundamentally, the findings on transillumination are uncertain because of the many variable factors: the intensity of the illumination, the darkness of the room, pigmentation of the skin, and the thickness of the facial