Objective: We aim to evaluate the effectiveness of the brush biopsy technique using OralCDx ® (OralScan Laboratories Inc., Suffern, NY) as a new method for early diagnosis and control of a 'potentially malignant disorder' such as oral leukoplakia. Design of the study: We performed a study in which samples were taken using OralCDx ® on 24 patients who visited the Master of Oral Medicine, Oral Surgery and Implantology of the University of Santiago de Compostela between February 2009 and May 2010. These patients presented clinical and histological lesions that were consistent with oral leukoplakia. We evaluated the relationship between the keratinization degree of the lesions and cell representation; the diagnosis obtained through OralCDx ® and biopsies; and sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). Results: 50% of patients were men and 50% women with an average age of 62.38 years. The Kappa coefficient relating keratinization of lesions and cell representation was 0.33, the OralCDx ® - biopsy diagnostic rate reached a Kappa value of 0.66, recording 72.7%, sensitivity and 92.3% specificity, PPV was 88.8%, while NPV reached 80%. Conclusions: cytology sampling with OralCDx ® showed high sensitivity and specificity values, which make it a good tool for monitoring oral leukoplakia, but nowadays the most reliable method that allows us to confirm the exact diagnosis of the lesions and their anatomical and pathological characteristics still is conventional biopsy using a surgical scalpel. © Medicina Oral S. L.