While CAR T-cell therapy continues to show promise, a key issue is toxicity. Here, Stanley Riddell, MD, of Fred Hutchinson Cancer Research Center, Seattle, WA., explains that these toxicities appear to be the result of dosage of T-cells administered, and better understanding of the pathogenesis of conditions such as cytokine release syndrome is crucial. Dr Riddell talks about the initiation of CRS and the role of adrenaline in its propagation. 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 European Hematology Association (EHA).