Background: Exposure of Genotoxic agents like formalin causes cancer. The duration of exposure and the quantity of exposure plays an important role in inducing the nuclear abnormalities. The nuclear abnormalities are BN, KR, KL.Objective: This study provides an easy and inexpensive way to assess the formalin induced nuclear abnormalities in different groups with different duration of exposure.Materials and methods: Fifty individuals with different duration of exposure were included in our descriptive study. Oral squamous cells were collected with the wooden spatula. The slides were fixed with methanol glutaraldehyde fixative and stained with Giemsa, May-Grunwald stains. After air drying, 1000 cells were screened for nuclear abnormalities like BN, KR, KL.Results: Nuclear abnormalities like KR, KL, BN were assessed. KL is more in less than 1-year exposure group.KR is more in long term exposure groups. BN cells are seen 6 -10 and 10 -15 years exposure group. Conclusion:The genotoxic effect of formalin was confirmed by the increase in the nuclear abnormalities especially by the increase in the frequency of KR in tong term exposed group and KL in less than 1-year exposed group.