With discovery of KIT (CD117) mutations and the advent of KIT tyrosine kinase inhibitor imatinib, there has been substantial improvement in overall survival in patients with advanced and/or metastatic gastrointestinal tumors (GIST). Recently, sunitinib showed activity as second-line therapy in GIST patients after failure with imatinib. However, virtually all patients will eventually progress or become intolerable after imatinib and sunitinib. In preclinical models, sorafenib inhibits KIT activity and cell growth of imatinib-resistant tumors. The objective of this multi-center, non-randomized phase II study is to evaluate the safety and activity of sorafenib given as third-line therapy for GIST.