We report a case of angiosarcoma with some peculiar clinical features developing on the left thigh of a 63-year-old man. The early primary lesion was erythematous with necrotic areas. The initial biopsy specimen of the lesion indicated a benign angioproliferative process. However, the necrotic area enlarged rapidly, ulcerated with severe pain, and thus was widely excised. The excised specimen had a malignant histologic appearance, particularly in the fascia, and was diagnosed as angiosarcoma. Following local recurrence, the lesion was complicated by thrombosis of the femoral artery at the affected site. A similar cutaneous lesion subsequently arose on the right lower leg, and thrombosis developed in the right femoral artery. Both legs had to be amputated. There were no distant metastases.