A 76-year-old woman developed angiosarcoma 11 years after a radical mastectomy in the chronic lymphedema of the ipsilateral arm, referred to as Stewart-Treves syndrome. The patient was treated by intravenous and intralesional injection of recombinant interleukin 2 (rIL-2; TGP-3, Takeda Chemical Industries, LTD, Osaka). Intralesional injection was more effective than systemic administration. After a month, the lesion where the local injection was done showed little tumor cells with a dense infiltrate composed of lymphoid cells. It was observed that NK activity, LAK activity and IL-2 receptor positive T-cells in the peripheral blood increased during the administration of rIL-2. As the lesion was too large to be treated with rIL-2 alone, radiotherapy was performed. But the patient had no remarkably improvement and died 16 months later from the onset. Immunotherapy with rIL-2 can be useful for angiosarcoma and more effective regimen of rIL-2 is a important problem.