Gastrointestinal stromal tumours (GISTs) are most common in the stomach (60-70%), followed by small intestine (20-25%), colon and rectum (5%), and esophagus (<5%). They are characterized by expression of the transmembrane receptor tyrosine kinase KIT, which is defined by the CD117 antigen and is the product of the kit proto-oncogene. Metastatic risk is based on tumour size and mitotic count. The treatment options have evolved rapidly with the discovery of imatinib (Gleevec) that selectively inhibits KIT. Complete resection without tumour rupture remains the mainstay of treatment in patients with localized, resectable disease. Imatinib has been shown to be the first successful systemic therapy for patients with metastatic or unresectable disease and is also currently being tested as an adjuvant therapy after the resection of high risk primary GIST. New blockers of the tyrosine-kinase activity are currently in development in cases of resistance.