The aim of this experimental study was to determine whether deep vein thrombosis (DVT) in animals occurs after osteosynthesis of the femur, and whether a postoperative drop in air pressure increases the frequency of DVT. Thus, osteosynthesis of the femur was performed in 10 New Zealand rabbits. Postoperatively a drop in air pressure of 300 hPA was induced. After 40 h in the pressure cabin ascending phlebography was performed (Group A). In a control-group of 10 other rabbits surgery was performed without postoperative drop in air pressure (Group B) while in a second control only the drop in air pressure was induced without surgery (Group C). The phlebographic studies showed DVT in 4 out of 10 rabbits in group A. In group B there was no demonstrable DVT while in group C one case of DVT was seen. The difference between group A and group B and C is statistically significant. In conclusion, a rapid drop in air pressure seems to have significant impact on the pathogenesis of DVT in rabbits after osteosynthesis of the femur.