AIM: To determine the proportion of women with abnormalities in cervical smears corresponding to borderline nuclear change, as defined by national guidelines, which return to normal or persist as cytological or histological abnormalities. METHODS: 313 women with borderline nuclear change diagnosed by a single pathologist using the national criteria were followed up for up to two years. RESULTS: On initial follow up, 45% of women had a negative smear or biopsy, 46.5% had a low grade cytological or histological abnormality, and 8.5% had a high grade abnormality. Of 81 patients in whom a second follow up smear or biopsy was available, 47% had no detectable abnormality, 38.5% had low grade lesion, and 14.5% had a high grade lesion. In total, 32 patients (10.2%) had a high grade lesion (defined as moderate or severe dyskaryosis on smear or CINII or CINIII on biopsy) on at least one follow up sample. CONCLUSIONS: The results support the use of the national criteria defining borderline nuclear change in identifying women at increased risk of developing a high grade cervical intraepithelial neoplasia, as identified histologically or cytologically, and highlight the importance of follow up in these patients.