Gastrointestinal stromal tumors (GISTs) are associated with a dismal prognosis in localized and advanced phase with a major resistance to conventional chemotherapy agents. Virtually all malignant GISTs actually harbor activating mutations of the KIT pathway in the tumor cells, leading to ligand-independent activation of KIT tyrosine kinase activity and tumor growth in vitro. Glivec® inhibits KIT and exerts a major antitumor efficacy in vivo in patients with advanced GIST. Glivec® is generally pursued until progression or intolerance. The optimal duration of treatment with Glivec® remains unknown. The objective of this study is to determine the feasibility of Glivec® treatment interruption with reintroduction at progression in GIST patients.