Purpose: To investigate the risk factor for prolonged intensive care units (ICU) stay in Korean. Methods: Data were extracted from V-SKI study (Validation of simplified acute physiology score 3 in Korean intensive care units) from July, 2010 to January, 2011. The data were established by respiratory failure research group including 15 hospitals. Prolonged ICU stay was defined as ICU stay ≥ 14 days. The data included demographic data, SAPS 3, SAPS II, and SOFA score. Results: In A total of 4,060 patents of ICU admission, male was 3,018 (63.9%)and mean age was 59.74±16.54 years. Mean duration of ICU stay was 8.65±17.67 day and patients with prolonged ICU stay were 504 (12.4%). SAPS 3 score was higher in patients with prolonged ICU stay than in patients with short term ICU stay (P＜0.001). SAPS II score and SOFA was high in patients with prolonged ICU stay (P＜0.001). The ROC of SAPS3 and SAPS II score for prolonged ICU stay were 0.684 (95% CI; 0.660-0.709) and 0.768 (0.746-0.789). Patients with prolonged ICU stay was older age (P＜0.001) and had higher frequency of cirrhosis, stroke, COPD, chronic pulmonary failure and metastatic cancer than patients with short term stay (P＜0.05). Emergency operation and acute infection were risk for prolonged ICU stay (P＜0.001). CPR and mechanical ventilator apply at ICU admission were more frequent in patients with prolonged ICU stay (P＜0.001). Conclusion: SAPS 3 score as well as SAPS II may help to predict for prolonged ICU stay. Clinician should have more attention and careful management of patient with high SAPS score.