As some lesions are less amenable to complete surgical excision, other treatment modalities have also been used. Simple aspiration runs a high risk for recurrence. One effective alternative is to sclerose the lesion with OK-432.1 OK-432 contains lypholized low-virulent group A Streptococcus pyogenes and benzylpenicillin, and it generates an inflammatory response, which involutes the cystic space without the induction of scarring.5 Owing to the induction of an inflammatory response, OK-432 injections can cause fever, pain, localized edema, and rarely cystic enlargement, leading to airway obstruction. These effects usually subside within 5 days. An injection may take 6 weeks to cause a response, and multiple injections may be needed. Only a few reports of successful OK-432 treatment for adult cystic hygromas exist.1,8 Successful treatment appears to correlate with simple macrocysts between 1 and 5 cm in size located below the mylohyoid.1 Other sclerosing agents such as alcohol, steroids, bleomycin sulfate, interferon, doxycycline, and cyclophosphamide have been injected into cystic hygromas with varying results.8 Owing to their less satisfactory recurrence rate, localized tissue damage, or systemic adverse effect profiles, these other sclerosants are rarely used.