Leiomyomas are bening tumours originated on smooth muscle. The most frequent site of appearance are uterine myometrium, gastrointestinal tract and skin. The highest incidence ocurs between 40 and 49 years of age. Its presentation is unusual in children or in older patients. Leiomyomas are unfrequent in the oral cavity, but in this location are usually localized on tongue, lips and palate. Leiomyomas use to appear as well-defined masses, with slow growth and totally asymptomatic. Pain is present just in rare cases. The treatment is surgical escision. Recurrences are extremely unfrequent. The diagnosis is mainly determined by histological studies due to its unspecific clinical appearance. Histopathologicaly proliferation of smooth muscle cells is observad without necrotic areas. A low number of mitotic figures can be seen. We present the case report of a 25-year old male patient, with a leiomioma on his right retromolar trigone.The low incidence of this pathology, the age of the patient and the inusual location, make the report of the case worthy.