Based on the histochemical scores and the statistical analysis, statistically significantly higher expression of ALDH1&2 was noticed in the leukoplakia group than in the lichen planus group (Pearson chi-square test, p=0.035) and in the erosive lichen planus group than in the mildly and non-dysplastic leukoplakia group (Pearson chi-square test, p<0.001). The gene discussed is ALDH1A1; the disease is leukoplakia.