AIMS: To analyse the current state of endometrial cytology practice by determining the interobserver variability in grading the atypicality of endometrial cells using kappa statistics. METHODS: A series of 70 clusters of benign, hyperplastic, and malignant endometrial cells on cytology specimens were examined by 19 experienced Japanese cytopathologists. They assigned each cluster to one of three diagnostic categories according to increasing cellular atypicality: negative for, suspicious of, and positive for malignancy. Each observer used their subjective judgement in grading without receiving any discriminatory criteria. RESULTS: Most classified the series of 70 clusters of endometrial cells into 33 negative, 20 suspicious, and 17 positive grades. However, observer variation was considerable, kappa statistics showing unfavourable overall agreement (kappa = 0.36). Although there was good agreement on negative and positive (kappa = 0.46 and 0.47, respectively), poor reproducibility occurred in grading suspicious ((kappa = 0.15). CONCLUSIONS: Currently, Japanese cytopathologists are not reliable in grading the atypicality of endometrial cells. This could be attributed mainly to the situation in endometrial cytology practice in which there are no generally accepted criteria for defining cells in which malignancy is suspected.