This collective review includes all available case reports of smooth muscle (stromal) tumors of the appendix and large intestine in the world literature. When compiling this review, we endeavored to examine cumulative as well as recently collected data on both benign and malignant smooth muscle tumors spanning the period 1875 to 1996. In total, there were reports of 331 leiomyomas (LMs) and 263 leiomyosarcomas (LMSs). The peak age of incidence of LM was 30 to 39 years, and the peak age of incidence of LMSs was 50 to 59 years. The female/male ratio was slightly higher for LM, and the male/female ratio was higher for LMS. The descending colon and sigmoid colon were the most common sites of both benign and malignant smooth muscle tumors. The growth of LMs most often occurred extraluminally, whereas LMSs tended to grow within the lumen of the colon. With both tumor types pain was the most frequent presenting complaint, followed less commonly by complaints of a palpable mass or gastrointestinal bleeding. LMSs tended to be larger at diagnosis than LMs, though the duration of symptoms for both types of tumor was most often reported to be between 1 month and 1 year. Finally, LMSs were found to metastasize mo