Meningiomas are generally sporadic and solitary tumours, but some rare cases have been known to be hereditary (Memon 1980; Conti et al. 1981; Ferrante et al. 1987). They occur particularly in patients affected by type 2 fibromatosis (NF2; Pansini et al. 1991). NF2 is a hereditary autosomal-dominant syndrome characterized by the occurrence of multiple tumours in the central nervous system, such as acoustic neuromas, meningiomas, ependymomas and gliomas. The NF2 gene, mapped to the long arm of chromosome 22 in 1986 (Seizinger et al. 1986), has been recently identified (Trofatter et al. 1993; Rouleau et al. 1993). Meningiomas are the most studied forms of tumours from a cytogenetic point of view. Chromosomic analysis performed on neoplastic tissue has shown the presence of chromosomic anomalies in the majority of cases. Among these, the total (monosomy) or partial loss of chromosome 22 constitutes a specific marker (Zang 1982; Casalone et al. 1987; Al Saadi et al. 1987). The complete monosomy of chromosome 22 has been observed in 20%–50% of cases documented in the literature, while deletion of the long arm of 22 (22q) with consequent partial monosomy is much rarer. It must be mentioned that normal karyotic meningiomas do exist, and that chromosomes other than 22 are sometimes involved (either in the presence or in the absence of monosomy 22). In the latter case the nonrandom involvement of chromosomes 8, 14, X and Y in numeric anomalies has been demonstrated, while chromosome 1 is involved in structural anomalies (Casalone et al. 1986; Al Saadi et al. 1987). The involvement of chromosome 22 in meningiomas has been confirmed in a molecular genetics study which demonstrated (by analysing the loss of heterozygosis of 22q with probe) that the partial or total loss of the long arm of chromosome 22 is a specific anomaly present in approx. 60% of these tumours (Seizinger et al. 1987; Dumanski et al. 1990; Wolff et al. 1992).