AbstractOnly recently has gastrointestinal stromal tumor (GIST) been recognized as the most frequent GI mesenchymal neoplasm. Prior to the use of KIT staining, most GI stromal tumors were identified as leiomyosarcoma (LMS). For primary GIST, surgery remains the principal treatment and adjuvant imatinib may improve outcomes. Multimodality therapy may also be effective in patients with metastatic GIST. In this review, we summarize the epidemiology, clinicopathologic features, natural history, and clinical management of LMS and GIST. J. Surg. Oncol. 2008;97:350–359. © 2008 Wiley‐Liss, Inc.