Despite the wide-spread opinion, that early stabilisation of femur fractures in multiply injured patients is of advantage, there are no publications that unambiguously prove this statement. In contrast, primary fracture stabilisation of the femur with concomitant thoracic trauma seems to increase the rate of complications. The biochemical data of the prospective study presented here suggest, that operative stabilisation of femoral fractures imposes an additional trauma on the already compromised organism. The period between days 2 to 4, when the primary activation of humoral and cellular mediators has returned to normal levels, seems to be the best time for osteosyntheses of these fractures. The operation in this period allows intramedullary fixation--the biologically and biomechanically best fixation procedure--with low risk.