Meningioma is a common tumor of the meninges covering the central nervous system. Although generally a benign tumor, meningioma often recurs and is malignant in 5-10% of all cases. Loss of chromosome 22 loci, and specifically inactivation of the NF2 tumor suppressor gene, is considered one of several critical steps in the tumorigenesis of meningioma. However, cytogenetic and molecular investigations have failed to detect either aberrations of chromosome 22 or mutations in the NF2 gene in approximately 40% of all tumors, thus making it apparent that an alternative mechanism(s) is responsible for the development of a large fraction of meningiomas. This subset of meningiomas is not distinct with regard to clinical and histopathological features from tumors showing deletions on chromosome 22. It is, therefore, important to attempt the elucidation of molecular pathway(s) that may operate in the tumorigenesis of these tumors. We used comparative genomic hybridization (CGH) to identify regions of the genome other than chromosome 22, contributing to the development of meningioma. We analyzed 25 tumors that had undergone detailed LOH analysis on chromosome 22 and were shown to contain no detectable deletions. Two benign, malignancy grade I, meningiomas showed concurrent deletion of 1p and 3p. These results suggest that loss of both 1p and 3p may contribute to meningioma tumorigenesis. This may represent genetic changes that are alternative to deletions on chromosome 22.