Despite a shortage of intensivists, there is an increased need for intensivist staffing in intensive care units (ICUs). Western studies showed that the survival rate of critically ill patients improved and the length of ICU stay decreased in "closed" or "high-intensity" ICU, where intensivists dedicated themselves to the ICU and were primary physicians. This system was also associated with an increased compliance of evidence-based medicine and a decreased medical error. The Leapfrog Group and American College of Critical Care Medicine recommend the implementation of intensivist staffing system in the ICU. Although there are still barriers to implement this system, such as the economic burden to hospitals and conflicts among medical staff, intensivist staffing in the ICU is important in terms of timely diagnosis and treatment and multidisciplinary team approach. The presence of intensivists may also increase the efficacy of ICU systems and save treatment cost. Although the "24 hours/7 days intensivist staffing" system may be ideal, recent data showed that high-intensity ICU system during daytime is not inferior to 24-hour intensivist staffing system in terms of hospital mortality. It is especially important to large-scale academic hospitals, where many severely ill patients are treated. However, few ICUs have intensivists who are committed to caring for ICU patients in Korea. Therefore, we have to try to expand this system throughout the whole country. Additionally, the definition of ICU standard, the role of intensivists, and the policy of financial reward also need to be clarified more clearly.