The authors report four cases of spontaneous retroperitoneal haematomas, which occurred in their department during a half year period. The patients were admitted from different internal medicine departments. They had anaemia, and bleeding with unknown origin and localisation, and were in a bad condition. Three patients could be suitable for operation after general preparation. One of these patients died and another one died without operation. Two of them went home after recovering. The patients were transferred to surgical department on average three days after the symptoms developed. Hypoprothrombinaemia was the reason for bleeding in three cases. One patient got overdosed Syncumar, and two patients suffered from alcoholic cirrhosis who had other serious diseases as well. The authors found that the fourth patient, who had the gluteal arterial rupture with inexplicable origin, also had hypoprothrombinaemia. It is very difficult to diagnose these disease. Bleeding always has to be taken into consideration, if the patients have liver disease, or any type of coagulopathy, or take some anticoagulant medicine. The blood test examinations, ultrasound, CT, MR, angiography, laparoscopy can be helpful in the diagnosis of these cases.