In order to increase the safety of the blood supply with respect to transmission of pathogens during transfusion, pathogen reduction methods are being developed and implemented. Photodynamic treatment (PDT) is among the approaches being studied. One PDT approach, the use of riboflavin and UV light (the Mirasol system) has been approved in Europe for pathogen reduction in plasma and platelet concentrates. It is in clinical studies for use in fresh whole blood and could also be applicable for red cell concentrates (RCC). Other approaches using PDT for pathogen reduction in RCC are described but none is currently in clinical studies.