The plasma of a peculiar strain of Brown Norway rats (BN/May Pfd f) is devoid of high molecular weight kininogen and poor in kallikrein. This strain could be used to estimate the involvement of the kinin system in inflammatory processes. In these rats, the oedema induced by kaolin, carrageenans, uric acid and urate crystals exhibited a small development, while the oedemas induced by 48/80, dextran, zymosan, trypsin, nystatin, concanavalin A and heating were not reduced. The exudates withdrawn from Brown Norway rats contained no kinin and a low level of PGE2. The involvement of the kinin system in these inflammatory models is discussed.