Our knowledge of Gastrointestinal Stromal Tumours (GIST) has been broadened in the last few years by the discovery of the key function of c-kit tyrosine kinase mutation in their pathogenesis. A single institution database is presented and a hypothesis is examined regarding probable connection between GIST and other gastrointestinal malignancies. Between 2000 and 2004 20 patients were admitted to our department with GIS tumour. With the addition of three cases detected between 1991 and 2000, and proved to be GIST retrospectively, 23 cases are followed. Mean age was 64.52 years, male to female ratio 11:12. Ten tumours originated from the stomach, ten from small bowel, one from rectum and two from mesenterium. All patients underwent surgery, 16 operations were completed with R0 radicality, one R1 and four R2 resections were performed. Follow-up ranged from 1 to 157 months. Five out of 23 patients died (21.7%), six patients live with metastatic disease, twelve are disease free. Amongst patient-, tumour- and treatment-related factors the prognostic significance of Fletcher's risk and radicality of resection was demonstrated (p0.05). Significantly more synchronous or metachronous gastrointestinal malignancies were found is this population of GIST patients, when compared to the prevalence of malignancies in normal Hungarian population (p0.001).