Objective:To determine the pharmacokinetics of continuously infused midazolam in patients during intensive care. Method: The study involved six critically ill patients who required sedation to facilitate controlled ventilatory support. The infusion rate of midazolam was adjusted individually to achieve an appropriate level of sedation. Blood samples were taken during and after the continuous infusion of midazolam to measure plasma concentration of midazolain with high performance liquid chromatography,and pharmacokinetic parameters were calculated. Result:The mean value of elimination half-life was 5.09 h(range: 3.19-7.30h), and the volume of distribution was 64.45L(range: 10.41-135.25L). The clearance was 7.29L/h, Conclusion:Clinical pharmacokinetics of midazolam in critically ill patients is highly variable. The increased volume of distribution in the patients is the major determinant for the slower elimination of midazolam.