Meningioma is a heterogenous group of primary brain tumors. The progression or recurrence is relatively very common; however, prognostic factors which may indicate those events are not known. The aim of the study was to evaluate the presence of mast cells within the low grade and high grade meningiomas. The material included 70 cases of meningomas (63 G1 grade cases) of adult subjects (range 23-84 years). In paraffin sections presence of tryptase, a marker of mast cells, was detected by immunohistochemistry in 10 random fields in each slide under the light microscope. The presence of the peritumoral oedema was estimated by brain computer tomography. The expression of tryptase was observed in 32% of low grade meningiomas and 86% of high grade meningiomas. The immunostained cells were observed close to the blood vessels. We conclude that the number of mast cells might be a significant prognostic factor for the recurrence or bad prognosis of meningiomas.