This is a non-randomized, open-label, multi-center, phase II study recruiting patients with advanced GIST who are pretreated with both imatinib and sunitinib. The current study will provide an estimate of the activity and safety of sorafenib in GIST. The primary study endpoint is the disease control rate (DCR), defined as complete or partial response or stable disease of at least 24 weeks of sorafenib therapy. Secondary endpoints include PFS, OS and safety.