In recent years, studies on the malignant potential of oral lichen planus (OLP) provided clinical evidence that patients affected by OLP have an increased risk to develop oral squamous cell carcinoma (OSCC); nevertheless, controversies still exist as to whether OLP has inherent predisposition to become malignant, or not. We believe extremely careful management of OLP patient is mandatory, and the aim of this paper is to illustrate our clinical guidelines in evaluating the possible risk of transformation in OLP lesions. Five-hundred and two patients (311 women and 191 men) affected by OLP regularly undergo follow-up examination in our Department. Patients' ages range from 18 to 83 years, with a mean of 55.4 years (57.5 for women and 53.9 for men); minimal follow-up period is 4 months, with a maximum of 12 years. In our group of OLP patients in the past 5 years we detected 24 carcinomas: excluding three cases in which diagnoses of OLP and OSCC were synchronous and three patients who had a history of tobacco use, thus possible malignant transformation of OLP would appear to be 3.7%. Clinical criteria used in our follow-up allowed us to detect 28.5% of tumours as in situ OSCC, 38% as microinvasive OSCC, 28.5% as stage I OSCC and 4.7% as stage II OSCC, with a remarkable improvement in prognosis compared to our previous study in which we adopted different criteria.