This paper describes blood sampling from the cranial vena cava (CVC) in the Norway rat. In order to limit stress, the blood sampling should be done under short-term inhalation anaesthesia, for example, an oxygen/isoflurane mixture. The injection site is just cranial to the first rib, 0.3-0.8 cm lateral to the manubrium when the animal is in dorsal recumbency. The needle, attached to a syringe, is inserted at 30 degrees in the direction of the opposite femoral head. After penetration of the skin, negative pressure is developed in the syringe and the insertion of the needle is continued for another 0.2-1 cm in the given direction until blood begins to flow. The amount of blood sampled ranges from 0.8 to 2.5 mL depending on the body weight of the patient. A trial on 50 rats aged 5-24 months included 25 rats sampled once, eight rats sampled twice with an interval of seven days, 11 rats sampled twice with an interval of three weeks and four rats sampled four times with intervals of four weeks--a total of 87 blood samplings. The serious complications quoted in association with blood sampling from the CVC in other experimental animals (vascular lacerations, heart puncture, serious haemorrhage, tracheal and throat trauma) were not observed in our study. There were only four blood samplings (4.5%) with mild haemorrhage from the injection site, due to erroneous sampling from the jugular vein.