Paraffin-embedded tissue blocks of 28 specimens of Non-dys OL, 33 of Dys OL, 9 of normal oral mucosa (NOM), 17 of inflammatory hyperplasia (IH), and 19 of oral squamous cell carcinomas (OSCC) were stained for Ki-67 and BMI-1 using immunohistochemistry. This evidence concerns the gene BMI1 and isolated hemihyperplasia.