A case of alveolar soft part sarcoma accurring in the abdominal wall in a 28 year old woman is reported. The mass was slowly growing during past 5 years to become hen egg sized. The lesion was suggested for a sort of malignant vascular neoplasm, clinically, on the basis of preoperative arteriographic findings, showing highly vascularized irregular mass fed by the right deep circumflexiliac artery with subsequent rapid venous drainage of pooled blood. Grossly, the mass was firm and measured 4.5×4.0×2.5㎝. The tumor was relatively well circumscribed except for areas where it blended into surrounding skeletal muscle. Cut surface showed pinkish gray in color with multifocal hemorrhagic microcystic appearances. Microscopically, tumor showed organoid arrangement of lobules separated by numerous delicate vascular septa. Individual tumor cell contained P.A.S. positive crystalline granules in the cytoplasm and prominent nucleolus. Brief comments on the histogenesis of this tumor, especially in relation to the vascular smooth muscle cell are made.