The occurrence of epidermoid cysts in the oral cavity is extremely rare. These cysts generally present slow and progressive growth and often are not diagnosed until the second or third decade of life. Epidermoid and dermoid cysts in the floor of the mouth are painless, doughy or fluctuant lesions and cause no symptoms until they are large enough to interfere with speech or eating. This article presents the case of a 20-year-old man with swelling in the floor of his mouth that was causing difficulties with speech and swallowing. After surgical removal of the cyst, histopathologic examination confirmed the diagnosis of epidermoid cyst. Characteristics of epidermoid cysts are described and surgical treatment discussed. Keywords: dermoid cyst, epidermoid cyst, floor of the mouth, sublingual, swelling