Intralesional injection of OK-432 was employed to treat 64 lymphangiomas between 1986 and 1992. This was used as primary therapy for 46 lesions (group A), as treatment following incomplete surgical removal in 14 (group B), and as therapy after failure of bleomycin in 4 (group C). In group A (n = 46), total shrinkage of the lesion, without serious complications, was noted in 23; there was marked shrinkage in 8, slight shrinkage in 12, and no response in 3. Of the cystic lesions (n = 24), significant shrinkage occurred in 22; of the cavernous lesions (n = 22), only 9 improved after treatment. In groups B (n = 14) and C (n = 4) there was significant clinical improvement occurred in 5 and 2, respectively. No recurrence was noted during follow-up (6 to 87 months). The only side effects were fever lasting 2 to 4 days and a local inflammatory reaction of 3 to 7 days' duration. The local inflammation did not cause any damage to the overlying skin and did not lead to scar formation. These data suggest that intralesional injection of OK-432 is effective treatment for lymphangiomas and should be considered as the primary method of treatment.