Objective: Peritumoral brain edema(PTBE) accounts for approximately 60% of meningiomas. It has not been identified why vasogenic edema, frequently shown in intra-axial tumors is also developed in extra-axial tumor such as meningiomas. Therefore, the authors assess the peritumoral brain edema of meningiomas with a focus on the angiographic pattern and expression of MIB-1 to clarify their correlation. Methods: A total 32 cases of meningioma was studied. The authors attempted to identify 1) the location of PTBE and the edema index (EI), 2) the location and dominancy of pial supply compared with meningeal supply, 3) the biological activity of meningiomas indicated by the MIB-1 LI (labeling index), 4) their interaction. Results: No PTBE was observed in the meningiomas without pial arterial supplement from internal carotid artery (ICA) and vertebral artery (VA). The PTBE of meningiomas with pial supply was developed intensely along the pial arterial supplement, and increased statistically in proportion to the extent of pial supply from ICA or VA rather than meningeal supply. Also, the MIB-1 LI in meningiomas tended to be larger in the tumors of the larger EI and the dominancy of pial supply. Conclusion: A strong correlation is found between the extent of PTBE in meningiomas and the dominancy of pial supply. The MIB-1 LI also tend to be associated with the PTBE. Therefore, the MIB-1 LI in benign meningiomas may represent not only the proliferative potential of the tumor, but also the biological activity like angiogenesis.