Leukoplakia is considered the most common and prevalent cancerous lesion in the oral mucosa, occurring preferentially in the male gender and age groups above 40 years of age. The etiology of this injury is not known, however, some factors are related to its pathogenesis, such as: smoking, alcohol, local chronic irritant modifiers (prostheses or poorly positioned teeth causing trauma), radiation UV light and microorganisms. Among the factors mentioned, one should pay attention to smoking, being strongly related as an etiological agent, because 80% of oral leukoplakia cases occur in smokers. The etiology of cancerous lesions is not well defined. Some risk factors such as alcohol and smoking or chewing tobacco play an important role in development of these lesions. The delay in the diagnosis made by the professional of health and the exposure of individuals to risk factors, such as smoking, alcoholism, genetic inheritance, viral infections, and excessive radiation exposure allow the malignant transformation, worsening the patient's prognosis. The present study aims to assess the prevalence of injuries potentially malignant in patients assisted in outpatient clinics belonging to a Hospital in Alfenas, MG.