Meningiomas are common intracranial and intraspinal tumors. They are treated primarily by surgical resection. Meningioma recurrence following surgery is frequent despite advances in microneurosurgery. However, it is not clear whether recurrent meningiomas, close or distant to the primary resection site, arise from incomplete resection, dissemination of tumor fragments or from independent tumor growth. In order to address the question of clonality in recurring meningiomas, we examined a series of five patients with a total of 14 tumors for X-chromosome inactivation in the tumor tissues. Four patients with a total of 11 meningiomas were informative for polymorphisms either in the PGK or the AR genes. All recurrent meningiomas were found to be clonal with respect to the primary lesions. This finding suggests a common molecular pathogenesis of primary meningioma and subsequent recurrences (p<0.01). In a sixth patient, we analyzed the NF2 gene for mutations in the primary and 5 recurrent meningiomas. All six lesions carried the identical NF2 mutation, strongly indicating a common origin for these tumors. We conclude that recurrent meningiomas usually arise from dissemination of tumor fragments, most likely at the time of the first surgical resection. Our data should alert to the potential of meningioma cells for seeding during surgical procedures.