Oral lichen planus is a chronic inflammatory cutaneous-mucosal dermatosis affecting the skin, appendages and mucous membranes, including the oral mucosa. These oral lesions pass through three phases: initial, state and late. During the active phase, lesions are bilateral and symmetrical, and are symptomatic. Positive diagnosis is based on the mandatory combination of clinical and histological criteria defined by the WHO. This condition requires symptomatic treatment and fairly cautious, ongoing monitoring, since lichen is classified as a disorder with malignant potential. the aim of this book is to detail the diagnostic and therapeutic approach to oral lichen planus.