On a neck lateral radiograph of normal person with the neck in full extension and with the best inspiratory effort, we could demonstrate three straight lines in the epiglottic area. The first line was the anterior margin of the epiglottis, which was well enhanced by air contrast in the vallecula. The second line was the posterior margin of the epiglottis, enhanced by air contrast in the larynx. The third line was the aryepiglottic fole. The purpose of this article is to provide objective signs for prompt recognition of epiglottic enlargement. We studied 150 cases without epiglottic enlargement and 10 cases with epiglottic enlargement. The result were as follows: The three lines were clearly seen as straight lines in 150 cases without epiglottic enlaargement. In 10 cases with epiglottic enlargement, line I showed obliteration(8) and anterior bulging (2), line II showed posterior bulging(7), blurring(2), and irregularity(1), and line III showed posteroproximal bulging(7) and irregularity(3). The causes of epiglottic enlargement were acute epiglottitis(7), hematoma(1), penicillin allergy(1), and carcinoma(1). In conclusion, any change in the three lines can allow the radiologist or emergency room physician to accurately suspect and alert the clinician to diagnose acute epiglottitis or other causes of epiglottic enlargement.