Objective: The aim of this study is to observe clinical effects of the millimeter wave on oral lichen planus (OLP) and its immune mechanisms.Methods: 30 patients with OLP were randomized into the millimeter wave group and the control group. 15 patients in the millimeter wave group were treated with millimeter wave (7.1 mm, 43 GHz, 10 mW/cm\+2) radiation, while the other 15 patients in the control group were just given soothing treatment. Either before or after the therapy procedure, the clinical manifestati...