By means of a standardized silver staining technique, nucleolar organizer region-associated proteins (AgNORs) have been demonstrated in paraffin sections of 41 astrocytomas and glioblastomas and 19 meningiomas. Computer-assisted image analysis was used to measure AgNORs together with other nuclear features. Significant differences in number and configuration of AgNORs have been found between non-anaplastic astrocytomas and anaplastic gliomata. In meningiomas, tumours with signs of increased proliferative activity and usual non-anaplastic ones could be discriminated using AgNOR data.