The micronucleus (MN) assay in exfoliated buccal cells is a useful and minimally invasive method for monitoring genetic damage in humans exposed to occupational and environmental agents. The MN test is used as an indicator of genotoxic exposition, since it is associated with chromosome aberrations. An increased mutation rate in oral squamous cells, which is indicated by an increased MN frequency, is also related to the development of oral mucosa diseases, such as carcinomas. We evaluated MN frequencies and other nuclear changes (NCs), karyorrhexis (KR), karyolysis (KL), broken egg (BE), and binucleus in buccal mucosa cells of 60 painters (30 smokers and 30 nonsmokers) and 60 healthy control subjects (30 smoker and 30 nonsmoker). Microscopic observation of 3000 cells per individual was performed in both painters and control subjects. In the control group and the exposed group, for each person repair index (RI) was calculated via the following formula: (KR + KL)/(BE + MN). The results showed a statistically significant increase in the frequency of MN in buccal epithelial cells of the exposed group compared with the control group (p < 0.05). Smokers and nonsmokers differed with respect to the incidence of MN and NCs in all groups. In painters, RI was less than that in the control group. There was a significant difference between painters and the control group (p < 0.01) for RI. We believe that determination of RI in addition to NCs and the MN will present a new approach to genotoxicity studies of a population.