Gastrointestinal stromal tumors form a small percentage of digestive tract tumors. They have recently been the subject of a new histopathologic classification made possible by immunohistochemical techniques. A series of criteria has been proposed which enables the identification of the most malignant and clinically aggressive tumors. We present five patients who were diagnosed with gastrointestinal stromal tumor, each of which had distinct characteristics. The different diagnostic tests performed, the difficulties of reaching a diagnosis as well as the treatment and distinct behavior of these tumors are discussed.