BACKGROUND: The laryngeal mask airway (LMA) has an established role in difficult airway management as a ventilatory device and airway intubator. It is ease to view the laryngeal aperature with a fiberscope through a laryngeal mask airway, so it offers a route to obtaining rapid access to the larynx. The objective of this study was to evaluate a narrowing degree of LMA by the epiglottis and to compare the intubation time and success rate of the blind intubation techinique with the fiberscope-guided intubation techinique through the laryngeal mask airway. METHODS: The LMA (#4) was placed into the hypopharynx after induction of anesthesia and muscle paralysis. The fiberscopic findings through the lumen of the LMA were recorded after the LMA placements. The degree of narrowing of the LMA by the epiglottis was estimated as 0%, 1 25%, 26 50%, 51 75%, or 76 100%. The breathing circuit of the anesthesia circle system was then disconnected from the LMA and a well-lubricated, cuffed, 5.5 mm ID endotracheal tube was inserted into the trachea through the lumen of the LMA either by the blind techiniques or fiberscope-guided techniques, and then intubation time and success rate were measured. RESULTS: The most frequent incidence (44/60, 73.3%) of narrowing by epiglottis in both groups was 76 100%. The success rate for fiberscope-guided intubation was 100%, while the success rate for blind intubation was 20%. The average intubation time of fiberscope-guided intubation was 26.0 s, while the average intubation time of blind intubation was 17.7 s. CONCLUSIONS: The fiberscope-guided tracheal intubation technique through the LMA is a more reliable method than the blind intubation technique through the LMA.