This lecture will describe what CAR-T therapy is, how it works and what it is used for. It will also review two common complications that might occur after treatment that might prompt patients to visit the emergency department (ED). These common complications are Cytokine Release Syndrome (CRS) and neurological toxicities. Common mimics of these toxicities will also be reviewed. And finally, the lecture will describe how to recognize and manage these complications in the ED.