Thirty-six fresh frozen plasma (FFP) units obtained from whole blood donations were used for 12 replicate experiments. For each replicate experiment, three ABO-matched FFP units were pooled and divided into three units containing different volumes of identical plasma. One unit was used as control FFP, one unit was treated with methylene blue plus visible light and one unit was treated with amotosalen and UVA light. The overall coagulation factor levels were better maintained in untreated FFP than in photochemically treated plasma. However, treated-plasma by both photochemical methods maintained coagulation factor levels that met or exceeded the European Pharmacopeia requirements for therapeutic plasma.