Occupational exposure to wood dust is associated with the occurrence of nasal cancer. In this study, we investigated micronuclei and nuclear changes (NCs: binucleates, karyorrhexis, karyolysis, and the "broken egg" effect) in exfoliated buccal cells of 20 workers exposed to wood dust and 20 age- and sex-matched controls. Micronucleus frequency and the frequency of each of the NCs were significantly higher for wood workers than controls (P < 0.01). Cigarette smoking was associated with increased frequencies of micronuclei and NCs in the buccal mucosa epithelium cells of both the control and exposed groups. Our findings indicate that buccal cells of wood workers display increased levels of genotoxicity and toxicity, and that these biomarker responses may be related to the increased cancer risk among wood workers.