In this video, Rose Ellard, MSc, Kings College Hospital NHS Foundation Trust, London, UK, outlines the importance of round-the-clock monitoring post-treatment for early recognition of toxicities. This video was recorded at the 1st European CAR T-Cell Meeting, held in Paris, France, co-organized by the European Society for Blood & Marrow Transplantation (EBMT) and the European Hematology Association (EHA).