The relationship between gastric mucosal hemorrhage and coagulation-fibrinolysis of fasting, restraint and water immersion stress (FS) rats was studied in comparison with normal (N) and fasting (F) rats. In this case, the FS group was fasted for 18 h prior to the stress application and then subjected to restraint and water immersion for various intervals. The F group was fasted for 18 h plus the time comparable to the stress load. Gastric mucosal erosions with bleeding were recognized from 1 h after the stress load only in FS group and the hemorrhagic erosion index progressively increased 1 to 16 h. In the FS group, prothrombin time and active partial thromboplastin time gradually prolonged with time course from 8 and 1 h, respectively, and plasma prothrombin level remarkably decreased from 1 h, although no changes in these parameters were observed in the F group. Plasminogen activator activity in gastric mucosa significantly increased in not only FS group but also F group from 0.5 h as compared with N group. However, no significant difference was seen between F and FS groups on this activity. Plasma plasminogen and antiplasmin levels in FS group were lower than those of N group, 3 h later. It is suggested from these results that sustained hemorrhage from the gastric mucosa in this stress ulcer may be associated with high fibrinolytic activity in the gastric mucosa and the delay of blood coagulation.