There are some diseases (called cystic diseases) which make cysts in Head & Neck area such as ranula. They are not tumors only collecting liquid inside the cyst wall. Though they are not malignant disease, only surgery had been thought to be a treatment. As for the operation, it was sometimes not easy because of very thin cyst wall or complexity (nearby important nerves and vessels) of operation area. And as for ranula, recurrence sometimes occurs if it was successfully removed. Additionally, operation scar sometimes might be conspicuous in Head & Neck area. We have applied OK-432 intracystic injection therapy for these cystic diseases since 1992. OK-432 intracystic injection therapy was started as a treatment of cystic lymphagioma (hygroma) first at Kyoto Japan in 1986. OK-432 intracystic injection therapy became to be a treatment of first choice for infantile lymphangioma in Japan now, and has come to be done world widely. Also, as for cystic diseases other than lymphangioma, we now think that this treatment can be a substitute for surgery from almost 20 years of experiences. Other than Japan, OK-432 therapy for ranula was also reported from Korea in 2006. I will explain this method for patients, their families and the people who are interested in this therapy as plainly as possible. I hope many patients will have the benefit of this therapy without fear. This is the aim to establish this page.