Benign or malignant smooth muscle tumors of the gastrointestinal tract are uncommon. The diagnostic and therapeutic approaches vary depending on the histological behavior of these neoplasms. Between 1981 and 1991, 32 patients with gastrointestinal tumors were treated at the Department of Surgery of the University of Patras. There were 16 females and 16 males. The mean age at the time of diagnosis was 61.9 years (range 22-83 years). Eighty-one per cent of the tumors were discovered in asymptomatic patients by a variety of diagnostic studies. Fifty-six per cent of tumors were located in the stomach, 38% in the small intestine and 6% in the colon. Leiomyomas made up 71.8% of these tumors and were treated by conservative excision. The malignant smooth muscle tumors were treated by radical excision in four cases and conservative excision in one case. The 5-year survival rate was 85% for leiomyomas and 0% for malignant smooth muscle tumors. There is widespread agreement that wide resection of the lesion is the appropriate treatment for these tumors. The size and mitotic activity of these tumors remain the most important diagnostic parameters and prognostic factors.