Objective: The dentist has a fundamental role in the early diagnosis of lesions of the oral cavity. The aim of this study was to establish the rate of erroneous clinical diagnoses and whether a clinical diagnosis is enough. The study was conducted to ascertain the overall accuracy of clinical diagnoses established by dentists. Study design: The biopsy reports of 1,566 samples taken from 1,406 patients and examined at the Dental Outpatients Department of the University of Padua from 1 January 2006 to 30 June 2012 were analyzed in order to compare the presumptive clinical diagnosis with the final diagnosis based on histology. Results: Overall, the dentists' clinical diagnoses were erroneous in 31.5% of cases. These diagnostic errors pertained to 23.8% of the benign neoplasms, 78.9% of the malignant neoplasms, and 17% of precancerous lesions. Conclusion: The present report should not be interpreted as a criticism of the clinicians making diagnostic errors but rather a confirmation of the policy to submit excised tissues for histologic examination. Keywords: clinical misdiagnosis, leukoplakia, oral cancer, oral examination, oral pathology, precancerous condition