The paper submits the results of the study of vascular models of experimental brain tumours in 20 Wistar rats and 20 rabbits from inbred races. These were transplantation tumours of the type of the dedifferentiated astrocytomas. First, the authors give a survey of the transplantation technique, the preparation of the vascular models and the advantages and disadvantages of the individual injection methods. The individual findings of the change in the blood supply of the brain, the vascular transformation by the tumour and the new formations of the tumour vessels are described and illustrated by pictures. Signs of true tumour vessels were: I. Caliber fluctuations, vascular occlusions and breaks; 2. Loss of direction property of the vessels, normal division and anastomosing; 3. Insufficiency of the vascular wall with extravasates and short-circuits; 4. Vascular bulgings with formation of pseudoaneurysms, meanders and blood puddles. The individual tumour vessel signs were found in a typical arrangement which permitted a classification of the tumour. Especially in the region of necroses and in the periphery of the tumour, the changes of the tumour vessels could not be strictly differentiated from reactive changes especially in the venous region.