A 44-year-old man with Menetrier's disease associated with protein-losing gastropathy and with abnormal serum complement profile is reported. He was treated by an antifibrinolytic compound tranexamic acid (trans-AMCHA) since he was found to have elevated fibrinolytic activity in the biopsied gastric mucosa. The therapy brought his serum protein from 3.8 g/dl to 5.6g/dl, however could not reduce his mucosal disorder. Substitution of a placebo for trans-AMCHA resulted in marked depression of his serum protein to 3.7 g/dl. It was concluded that trans-AMCHA was effective in raising his serum protein to a certain extent but failed to block the vicious circle of "mucosal disorder", "increased tissue fibrinolysis" and "hypoproteinemia" (Kondo, M. et al. Gastroenterology 70, 1045, 1976). Abnormal serum complement profile seen in this patient was found to be due to cold activation of the classical complement pathway (Kondo, M. et al. J. Immunol. 117, 486, 1976). Although no correlation between the phenomenon and Menetrier's disease has been clarified yet, the appearance of wheezing as in asthma when exposed to cold suggested that cold activation of complement occurred in vivo and resulted in increasing of the vascular permeability in the lungs.