Meningiomas more often behave as benign tumors although their very rate of recurrence is unknown. These neoplasms have been exhaustively studied but neither their subtypes nor their histologic features were ever considered as reliable data of their biologic behavior. Different types of assays have been achieved in order to assess the aggressiveness of these neoplasms. The first one concerned the mitosis index and different markers of proliferation. Other ways have been explored as the dual expression of the differentiation and the steroid receptors of the neoplasms, with no evidence of a clear cut prognostic value. Aneuploidy is thought to be associated with a rather poor behavior, and chromosome 22 is the most frequent abnormality. Recent studies on growth factors related with some of the factors previously mentioned and expression of oncogenes complete the overview of the methods involved in the search for prognostic data.