PURPOSE: To evaluate the efficacy of OK-432 solution for sclerotheraphy of cystic lesions of the head and neck. MATERIALS AND METHODS: Nineteen cystic lesions comprising ten plunging ranulas, three simple ranulas, three cystic lymphangiomas, one first branchial cleft cyst and two unknown supraclavicular cysts considered to be lymphangiomas were treated by sucking out as much liquid content as possible and then injecting the same volume of OK-432 solution under ultrasound guidance. Patients were followed up clinically and radiologically. RESULTS: Follow-up sonography or CT performed after a mean interval of nine months showed total or near-total shrinkage of four plunging ranulas. However, six such lesions recurred in spite of more than one (mean, two) sclerotherapy sessions. In cases involving two simple ranulas at the floor of the mouth, failure resulted from extracystic leakage of OK-432 solution via the puncture site. Two unilocular cystic lymphangiomas completely regressed during the follow-up period (mean, seven months), but the multilocular type showed a 65% volume reduction after 12 months. A first branchial cleft cyst was markedly reduced in size, with only a small cystic portion remaining after eight months, follow-up. Two supraclavicular cysts with straw-color fluid did not respond to sclerotherapy. CONCLUSION: OK-432 sclerotherapy of macrocystic lymphangiomas is an effective and promising alternative to surgery. For other cysts, however, including plunging ranula, efficacy varied, and 64% of such lesions recurred.