The present study describes a new in vivo animal model that enables the detection of cerebrospinal fluid (CSF) leakage after dural injury. A polyethylene catheter (PE 10) was inserted into the subarachnoid space in the lumbar area by a simple surgical procedure and a radioactive isotope Tc99m Macroaggregated Albumin (Tc99m MAA) was injected into the CSF. In the experimental group, a standardised dural puncture was performed in the cervical area. The accumulation of the isotope in the gauze placed over the dural puncture and viewed by a gamma camera as a spot of concentrated radioactivity, was indicative of CSF leakage. In a second group of animals with intact cervical dura the absence of leakage was presented as a picture of sporadic background radioactivity. To demonstrate the effectiveness of the model in detection of invisible leakage, blood was applied over the cervical dural defect in another group of animals and CSF leakage was assessed by the above mentioned isotope detection method. This in vivo model may be used for evaluation of the sealing properties of various materials under physiological and metabolic processes in living tissue.