leukoplakia,erythroplakia and palatal changes due to reversed smoking(R.S) are considered as precancerous lesions .oral lichen planus has been considered as a precancerous condition.to evaluate 
precancerous lesions in factory workers of Kerman city,a cross sectional study was designed in which 1167 workers(1070 men,97 women,mean age=31.8) were participated.dental mirrors,explorers and flashlight were used for oral examinations and all the workers were examined by one person.overall 115 persons 9.9% had red and white lesions and among them 43 cases (3.7%) of precancerous lesion and 6 cases (0.5%) of lichen planus were diagnosed.all biopsy speciemen showed nondysplastic leukoplakia.direct relationship was observed between cigarrette smoking habits and loukoplakia(p<0.001).there was also a reverse relationship between educational level and leukoplakia(p<0.001).loukoplakia and lichen planus were most prevalenced in the age group of 20-40 years(p<0.001). also most of the lesions were detected in buccal mucosa and vestibule.Erythroplakia and R.S were not observed at all.the study showed a high rate of precancerous lesions among the workers (3.7%).further epidemiological studies of oral precancerous lesions and the inclusion of intraoral examinations in health care programs are recommended.