In an interface between brain tumour and surrounding tissue there occur simultaneously two very important phenomena. On the one hand there is a proliferation of peritumoral vessels penetrating into the neoplasm in which they make alike tumoral vessels. On the other hand, neoplastic cells penetrate from the tumour into the vicinity along peritumoral vessels. To determine the influence of the histological type of different brain tumours, their malignancy degree as well as location in the central nervous system on peritumoral vessels morphological appearance, the detailed morphometric analysis was carried out. The morphological examination and computerised morphometric analysis were conducted on 166 primary and metastatic CNS neoplasms taken during routine neurosurgical procedure. It turned out that the peritumoral angiogenesis depends predominantly on the malignancy of brain tumours. This angiogenesis may be modified by local environmental factors--it is more evident within the white matter than in the cerebral cortex. One of the important factors may be reactive peritumoral astrogliosis. There is no specific CNS region predisposed to the development of peritumoral angiogenesis.