In this study we investigated the accuracy of diagnoses of oral mucosal diseases made by family physicians (without a dental degree), other categories of physicians, and general dental practitioners prior to referring patients to a university oral medicine unit. Over a three-year period, we compared the diagnoses proposed in referral letters with the definitive histological diagnoses made by the specialist unit. Only 305 of 678 (45 percent) of the referral letters included a clinical diagnosis. Eighty-six patients (86/305, 28 percent) were referred by general dental practitioners (GDPs) who had graduated in dentistry; seventy-six (76/305, 25 percent) were sent by GDPs who had graduated in medicine with a postgraduate degree in dentistry; and 143 (143/305, 47 percent) were referred by other categories of physicians. More than 50 percent of the referring professionals were not able to make a clinical diagnosis of oral mucosal diseases. Only 40 percent of the provisional diagnoses (122/305) coincided with the diagnosis made at the specialist unit. The proportion of correct diagnoses was 40 percent for GDPs who had graduated in dentistry, 33 percent for other categories of physicians, and 27 percent for GDPs who had graduated in medicine with a postgraduate degree in dentistry. These findings suggest that Italian dental and medical practitioners have limited knowledge in the field of oral medicine. Consequently, there is a need for better education in the diagnosis and treatment of oral diseases and for improvement in total oral health training.