In the intensive care unit (ICU), neuromuscular blocking agent (NMBA) is occasionally used with sedatives and/or analgesics, for the management of mechanically-ventilated critically ill patients. For its application in ICU, close attention should be paid on the side effects unlikely seen during operation because the basal conditions of ICU patients are more serious and its infusion period is likely to be long. There have been reports of the prolonged weakness after the long term use of NMBA. The incidence of prolonged weakness increases when a corticosteroid is applied concurrently. These side effects are associated with increases in ICU and hospital stays, and healthcare costs. Strategy should be focused on its prevention. For example, routine monitoring with peripheral nerve stimulation and titration to the minimum dose of requirement, are relevant and effective. The application of NMBA in ICU is reviewed and rocuronium recently placed on market is within the scope of this article.