Abstract: The chromosomal analysis of cultured peripheral blood lymphocytes from 18 patients with oral lichen planes (OLP) and 20 heaply controls was carried out by G-banding teclmique. The lymphocyte transformation rate was investigated in 11 of the OLP patients and 11 healthy controls. It was found that the structotal aberration rate of chromosome in OLP patients was significantly higher than that of control group (P<0.01). It suggested that the patients' chromosome was unstable snd there might be a risk of malignant transformation in OLP. It was detected that the aberration frequency of No.2 chromosome was the highest in the OLP patients. Its significance was not clear. But no significant difference in lymphocyte transformation rate was found between the two groups.