Effective invasive and non-invasive monitoring, when coupled with good clinical decision making, can improve outcomes for critically ill patients. When deciding on the best monitoring technique, it is important to consider the specific information that is needed to guide critical care management, while balancing the reliability of the data obtained and the risks of invasive monitor placement. Here, we review invasive and non-invasive options for hemodynamic and neurologic monitoring in the Surgical Intensive Care Unit. Understanding how each monitoring device functions, its indications, risks, and limitations is key when deciding how to monitor bedside physiologic data that guide clinical decision making. Level of evidence: Level IV