In consequence of the increasing osteosynthetic treatment of bone fractures we draw the attention to iatrogenic blood vessel injuries. Primary location is the proximal thigh. Most important is the clinical diagnosis of an acute ischaemia of the operated limb. An arteriographic diagnosis is not necessary, but the operation site should be explored immediately. Prevention of intraoperative lesions of great vessels consists of exact anatomic reposition of the bone fragments, a subtile osteosynthesis whereas the osteosynthesis material should not extend the bone cortex. Exact haemostasis should be performed, avoiding extending ligations. Intraoperative as well as postoperative control of peripheral pulses should never be omitted.