A silver staining technique was used in the study of nucleolar organizer regions (Ag-NORs) in paraffin sections of 40 meningiomas. The specimens were divided into three groups as follows: typical (n = 24), atypical (n = 8) and recurrent (n = 8) groups, and the mean number of Ag-NORs was evaluated in three groups. The mean Ag-NORs number (mean +/- S.D.) of typical, atypical and recurrent group was 1.48 +/- 0.14, 1.82 +/- 0.16 and 2.05 +/- 0.23 respectively. The mean Ag-NORs number of atypical and recurrent groups was significantly greater than that of typical group. These results suggest that the proliferative potential of meningiomas and the risk of recurrence could be evaluated by quantification of Ag-NORs.