The plunging ranula is a mucous extravasation cyst of the sublingual gland. It is slightly more common in females, shows no side preference, and is more prevalent in the second and third decades of life. It typically manifests as a painless, nonmobile swelling in the neck and in four of five cases is associated with an intraoral ranula or swelling. If there is no history of an oral ranula the clinical diagnosis is difficult, and it may be left to the reporting pathologist to give the correct diagnosis. The histologic appearance is characteristically of a cyst, devoid of epithelium or endothelium, with a vascular fibro-connective tissue wall containing some chronic inflammatory cells and macrophages stuffed with mucin. The correct diagnosis is essential for the most effective treatment, which is excision of the sublingual gland.