AbstractThe objective of this study is to evaluate the role of micronuclei (MN) in identifying the atypical urothelial cells urinary cytology. This is a retrospective study of a total of 30 cases of urine samples. Of these, 15 cases were selected where the initial diagnosis was atypical urothelial cell and later turned out as malignant cells on follow‐up histopathology. The rest of the 15 cases were reported as normal urothelial cells. The number of MN in 1,000 urothelial cells was counted in all the cases and was expressed as percentage. All the cases diagnosed as atypical urothelial cells show the presence of MN. The mean number of MN was 2.53 ± 0.99%. No MN was noted in any of the normal urothelial cells in control cases. The Student's t‐test of MN scoring was highly significant (P < 0.000) in test (atypical urothelial cells) versus control group (benign urothelial cells). MN is an important biomarker of malignancy. Micronuclear score in atypical urothelial cells in urine cytology smears may help in proper diagnosis of the case. Diagn. Cytopathol. 2010;38:811‐813. © 2010 Wiley‐Liss, Inc.