Argyrophilic nucleolar organising region associated proteins (AgNORs) are of interest in a variety of diseases including thyroid disorders. We have investigated the cut-off values for AgNOR count and with a new approach, Total AgNOR area/nuclear area (TNORa/Na) proportions to discriminate thyrocytes obtained from benign thyroid nodules and normal thyroid tissue. Thirty patients whose fine needle aspiration (FNA) materials were compatible with a benign lesion (named as goiter group) and 30 controls (subjects with normal thyroid tissue) were included. In the control group, biopsy material was obtained from histologically normal thyroid gland operated on because FNA material was compatible with papillary thyroid carcinoma (PTC). These samples were stained for AgNOR and 100 nuclei per individual were examined. Both AgNOR values for individual cells and cut-off values were detected for each group. Patients with goiter had significantly (P<0.001) higher AgNOR count (2.1 +/- 0.6%) and TNORa/Na (6.1 +/- 1.5%) than the control groups (1.4 +/- 0.2 and 3.0 +/- 0.4, respectively). The cut-off values were <1.5 for AgNOR count and <3.8 for TNORa/Na in thyrocytes of the controls. This modified method is an easy and reliable method for discriminating various thyroid disorders, including the differentiation of benign thyroid nodules from malignant ones. It also helps to discriminate thyrocytes obtained from benign nodules from normal thyroid tissue, aiding accurate localisation of sampling in FNA material.