Introduction: Rapid response team (RRT) screens high risk in-hospital patients and provides acute managements for prevent-ing clinical deterioration of them prior to cardiac arrests. Screening of high risk patients is important issue in activity of RRT. Modified Early warning score (MEWS) has been used for this activity in many hospitals but the role has not been proved well in medical and surgical in-hospital patients. Aim: We aimed to evaluate the use of the MEWS as a screening tool of identification of medical and surgical patients who require acute managements for preventing in-hospital death. Methods: Clinical parameters were evaluated from 339 patients for 2 months in one university hospital. All high risk patients were screened and monitored by a pulmonologist, a cardiologist, a resident and a nurse. We made "call criteria" using of lab data, vital sign and emergent consults. MEWS were calculated from the data and multivariated regression analysis was per-formed to identify related factors including in-hospital mortality. Results: 135 surgical and 193 medical patients were evaluated. Male was 163 (48.1%) and mean age is 62.6±16.4. None of patients with lower MEWS (≤1) got emergency procedures but patients with MEWS ≥2 had 54 emergency procedures. We found 8 in-hospital deaths in patients with MEWS ≥2 but none in patients with lower MEWS. Conclusion: The MEWS may used as a rapid screening method to identify high risk patients. Patients with lower MEWS did not need procedures for preventing cardiac arrest and it means that lower MEWS could be used as an exclusive tool for screening high risk patients who need emergency procedure for preventing cardiac arrests.