Serial changes of activated factor XIII (XIIIa), alpha 2 Plasmin inhibitor (alpha 2PI) and fibronectin (FN), which have important role in wound healing and host defence mechanism, were studied in 27 trauma patients. We obtained the results as follows. 1) The alpha 2PI and the FN decreased in proportion to injury severity score (ISS) immediately after trauma and they increased statistically significantly on the second or the third hospital day. On the other hand the XIIIa showed no statistically significant changes after trauma. 2) Emergency operations performed on the first hospital day had no influence on the variations of the XIIIa, the alpha 2PI and the FN. 3) The patients with disseminated intravascular coagulation (DIC) showed statistically marked decrease of the XIIIa, the alpha 2PI, and the FN on admission and the first hospital day compared with those patients without DIC. On the second hospital day, there was no difference of these factors between the DIC patients and the patients without DIC, but on the following day the alpha 2PI and the FN decreased again. In conclusion, the alpha 2PI and the FN decrease in proportion to ISS but XIIIa shows no significant changes after trauma. Emergency operations have no influence on the variations of these factors but with complicating DIC, all of these factors decrease significantly.