BACKGROUND: Surgical tracheostomy(ST) is usually performed by surgeons in operating room. For a patient with mechanical ventilation, however, transportation to operating room for ST could be dangerous for patients. In addition, ST is often delayed due to unavailability of operating room or surgeon. Percutaneous dilatational tracheostomy (PDT), although novel in Korea, is gaining popularity as a bedside procedure in the hospitals of western countries. We evaluated the technical ease and safety of PDT in comparison with ST. METHOD: Thirty-eight patients in medical intensive care unit (ICU) who were either under mechanical ventilation for more than 7 days or required airway protection, were randomly assigned to ST(18 patients) or PDT(20 patients). Between two groups, there was no significant clinical difference except that female to male ratio was higher in the ST group. ST was performed by second year residents of the department of otolaryngology while PDT was performed by third grade medical resident and pulmonologist under bronchoscopic guide using Ciaglia Percutaneous Tracheostomy Set (Cook Critical Care, Bloomington, USA) in medical ICU. The following factors were compared between two groups : number of delayed cases after the decision for tracheostomy, procedural time, complications related to tracheostomy. RESULTS: Delayed cases were 11 in ST group and 3 in PDT group (P<0.05). Procedural time was significantly shorter in PDT group (15.6+/-7.1min) than in ST group (29.1+/-11.6min, P<0.0001). Complications related to tracheostomy occurred in 5 cases in ST group : accidental decannulation (1), subcutaneous emphysema (2) and minor bleeding (2), and in 4 cases in PDT group : minor bleeding (2), subcutaneous emphysema (1) and premature extubation (1) (P>0.05). CONCLUSION: Since percutaneous dilatational tracheostomy was easy to practice and its complications wert not different from surgical tracheostomy, PDT can be a useful bedside procedure for mechanically ventilated patients.