A 36-year-old man was admitted who had a 2-month history of swelling of the right submandibular area and the right side of the mouth floor. He had undergone operations for right plunging ranula with a lesion on the floor of the mouth twice 7 years ago. Under fluoroscopic guidance, the contents of the cyst were aspirated as much as possible and injected with the same amount of OK-432 solution (Picibanil 0.1 mg; 10 ml) twice with 3-week intervals. Examination after 6 weeks showed that the cystic mass seen before therapy had disappeared completely, and no recurrence was encountered after 1 year. We here report a case in which a successful sclerotherapy with OK-432 for recurrent plunging ranula after surgery was performed.