The aim of this article was to present a case of gastrointestinal stromal tumour (GIST) presenting with acute intestinal bleeding. The Authors outline the histogenetic, clinical, diagnostic and prognostic profile of this pathology. Technical progress in immuno-histochemical and ultrastructural diagnostics has made possible to go beyond the old definition of gastrointestinal stromal tumours and identify several subgroups of such tumours on the basis of nervous and/or muscular phenotypic differentiation. The histopathological and structural variety of GIST accounts for their different clinical manifestations and variable and unpredictable biological behaviour. Histological criteria are by no means of absolute value: tumours considered benign on the basis of histology may present a malignant behaviour in the course of time, with the development of metastases and recurrences. In this regard, a number of predictive malignancy indices have been identified such as the patient's age, tumour size, presence of haemorrhage and necrotic areas, high mitotic index (> 5 mitoses/50 HFP), and kit-gene mutations. The Authors stress the diagnostic importance of 99m Tc-RBC scintigraphy in the case reported and agree with the literature as to the appropriate therapy, consisting in intestinal resection. The therapy of active GIST is essentially surgical and consists in resection of the intestinal tract affected by the tumour: lymphadenectomy must be performed only in case of need, because GIST metastasis preferably via the blood stream. As far as therapy is concerned, the demonstration of kit-gene mutation, expressed by the more aggressive forms, has made it possible to produce an inhibitor of protein tyrosine kinase Ber-Abl, which causes selective inhibition of cellular proliferation both in vitro and in vivo and induces apoptosis of Ber-Abl positive cell lines.