This study was designed to investigate the fitness of stock tray in Korean adults. 107 dental students (male: 87, female: 20) who have normal occlusion and symmetric facial fom were selected. The upper and lower stock tray (Osungtray, Osung Co., Korea) fit with dental arch were selected for taking irreversible hydrocolloid impression. The author measured the thickness of impression material about two items, that is, width and length on the flange of stock tray. Several measuring points on the dental arches and palatal area were checked with Goldman Fox prove (Hu-Friedy, U.S.A.). The obtained results were as follows: 1. The width of impression material on buccal flange of upper and lower trays were narrower than any other measuring point, but the thickness of impression material on the palatal area of upper stock tray was the widest of all measuring points. 2. The length on buccal flange of lower stock tray was shorter, but the length on tray flange of lower stock tray at lingual frenum area was longer. 3. On upper dental arch, the upper extra-large tray was used in 53% of subjects, but upper small tray was not used. 4. On lower dental arch, the large tray was used in 55% of subjects. 5. There was not adequate tray on upper dental arch in 4 subjects.