Since the first single patient with metastatic GIST treated by Glivec® in March 2000 (16), more than 2000 patients have been included in prospective trials testing activity and tolerance of Glivec® in patients with advanced/metastatic GIST. High response rates have been documented, only a limited percentage of patients progressed after achieving objective response, and median survival has not been reached in all studies. There has been no clear demonstration of a dose-response relationship. About 15% of patients experienced a rapid disease progression under treatment but the mechanisms of resistance remain unknown. Some patients progressing at 400 mg/day further responded to higher doses of Glivec®. Toxicities were infrequent, mainly mild to moderate and their incidence seems to be related to the total daily dose administered.