Nucleolar organizer regions (NOR) are chromosomal segments in which ribosomal RNA is encoded. AgNOR technique, which reveals these regions, has rarely been used in the diagnosis and preceding the prognosis of pituitary adenoma. The purpose of this study was to determine and evaluate the correlation of hormonal profile with AgNOR counts, the correlation of recurrence with AgNOR counts, and to determine the consistency between the evaluations of the two independent observers. This study covers 33 patients with pituitary adenoma. The slides were stained with hematoxylin and eosin. Silver colloid method was used for NOR, and immunohistochemistry for hormone expressions. Consistency was significant between the two pathologists (for hormonal profile, the Kappa test was used and P < 0.001; for AgNOR count, intra-class correlation coefficient was 0.83). There was no significant correlation between mean AgNOR counts and hormone expressions (P > 0.05), and there was also no correlation between mean AgNOR counts and tumor sizes (P > 0.05). While no difference between recurrent and non-recurrent patients was found with respect to mean AgNOR numbers (P > 0.05), nucleolar silver staining in the form of AgNOR clusters was more frequently detected in recurrent cases. (C) 2002 Elsevier Science B.V. All rights reserved.