Evidence has emerged that suggests adverse effects to perioperative homologous blood transfusion are related to the age of the blood products. Recently, time-dependent accumulation of bioactive substances in red cell suspensions, standard platelet concentrates and fresh frozen plasma during storage have been shown. The potential adverse effects of these bioactive substances were analysed in a burn trauma patient. A patient with 40 per cent second and third degree burn trauma without other injuries underwent a two-step transplantation operation. Samples for analyses of histamine, eosinophil cationic protein (ECP), eosinophil protein X (EPX), neutrophil myeloperoxidase (MPO) and interleukin 6 (IL-6) were drawn frequently from the patient before, during and after the operations, and from all transfused red cell, platelet and fresh frozen plasma units. Urine was sampled every hour during the first operation for analyses of ECP and EPX excretion. All analyses were performed by ELISA and RIA methods, and results compared to patient outcome. The patient received a total of 48 and 8 SAGM blood, 6 and 0 platelet and 12 and 4 fresh frozen plasma units at the two operations, respectively. Transfused products contained a total of 64.54 nmol and 17.50 nmol histamine, 115518 ng and 25764 ng ECP, 174457 ng and 38770 ng EPX, 6950915 ng and 1505125 ng MPO, and 14740 pg and 5600 pg IL-6 at the two operations, respectively. The accumulation of the substances in patient plasma correlated to postoperative septic reactions, without any disclosure of bacteraemia after the first operation, while the accumulation at the second operation correlated to the septic reaction and Pseudomonas aeruginosa infection. Time-dependent accumulation of bioactive substances in blood products during storage may be related to the development of post-transfusion adverse effects.