This research was to study the treatment and therapeutic drug monitoring of vancomycin, one of the most prescribed antibiotics in pediatric intensive care units in US hospitals, from a system-level perspective. A mixed-method approach was used including a workflow study (chapter 3), an informatics study (chapter 4), and a simulation study (chapter 5) to identify and evaluate discrepancies in the treatment process and the impact of such on therapeutic drug monitoring for vancomycin.