Malignant mesenchymoma is a rare tumor formed by two or more unrelated mesenchymal tissues, disregarding the fibrous component that is usually present ot some extent. The tumor is found in all ages and locations, but most occur in the deeper structures of the extremities and in the retroperitoneum. The biologic behavior of the malignant mesenchymoma is characterized by rapid growing and, non responsiveness to all modes of therapy. We experienced a case of malignant mesenchymoma in 33 years old woman. Grossly, submitted specimen consists of a huge, capsulated tumor mass with attached kidney. The tumor mass measures 20×17×16㎝, and 1850gm in weight. Microscopically, sections revealed a sarcoma exhibiting areas of liposarcoma and rhabdomyosarcoma.