Gastrointestinal stromal tumor (GIST) is the most frequent mesenchymal neoplasm of the gastrointestinal tract. Now, there is widespread scientific and clinical interest in GIST because of identifying in principal pathogenetic defects and development of a specific molecular inhibitor of GIST. GISTs have a gain-of-function mutation in the c-kit protooncogene. Mutation results in constitutive activation of the Kit receptor tyrosine kinase, which induces malignant cell proliferation. Imatinib (gleevec) is an oral agent that selectively inhibits c-Kit, whose efficacy proves that a specific inhibitor can counteract the effects of a genetic defect responsible for cancer. Although STI571 was first applied to GIST, it has already revolutionized the treatment of patients with metastases. Now so many molecular target agents are under development in clinical trials.