OBJECTIVE To study the time course and correlation of prothrombin fragment (F1 + 2) in plasma and urine during THA. METHODS F1 + 2 concentrations were recorded at four time-points during THA. RESULTS F1 + 2 increased during surgery. In contrast to urine, plasma F1 + 2 was temporarily reduced the first postoperative day. At day six, plasma F1 + 2 was significantly elevated indicating on-going thrombin activation, while urine F1 + 2 was normalized. CONCLUSIONS The response in coagulation to operative trauma can be recorded with F1 + 2 both in plasma and urine. We were not able to demonstrate any correlation of F1 + 2 in plasma and urine later in the postoperative period.