Although surgical excision has been considered to be the treatment of choice by most of the surgeons, sclerotherapy of lymphangioma has gained popularity during recent years. A prospective clinical trial was conducted to evaluate the efficacy of bleomycin and OK-432 sclerotherapies for treating lymphangioma in children. Fifteen patients were enrolled in the study conducted between 1998 and 2002. All patients were hospitalized. Bleomycin or OK-432 was injected into the lesion. Patients were observed in the hospital for 1 day. The response was considered as excellent in cases with total disappearance of the lesion. If the lesion was regressed more than 50% of the original size, the response was considered as good. Little or no change in the size of lesion was considered to be a poor response. Ten girls and five boys with ages ranging from 4 days to 12 years were treated. Five patients had been operated previously for lymphangioma. Most of the lesions were located only in the cervical region (n=13). Other cases revealed extensions into the mediastinum (n=1) or axilla (n=1). Bleomycin (n=8, 2.87+/-2.03 inj.), OK-432 (n=5, 2+/-1 inj.) or both in order (n=2, 6 and 16 injs.) were injected. No allergic reaction, scar formation or pulmonary complication was encountered. Fever (11%), local reactions (4%) and vomiting (2%) were encountered following a total of 55 injections. After a follow-up period of 6-36 months, the responses were excellent in 53.4%, good in 26.7% and poor in 6.6%. Macrocysts disappeared in the remaining 13.3% of patients who had mixed cervicofascial lymphangioma. Lower success rates were encountered among patients who had undergone prior surgery. Sclerotherapy with bleomycin and OK-432 is effective in the treatment of lymphangioma in children. Adverse effects are minor and rarely encountered. However, the surgeon should be alert for the possible serious complications. Sclerotherapy can be also used as an adjunctive therapy in the treatment plan of widespread or mixed forms of lymphangiomas. In the light of our results, sclerotherapy should be preferred as the primary mode of treatment in childhood lymphangiomas.