Gastrointestinal Schistosomiasis and Amebiasis are uncommon in the western world, while such infections are frequent in the African community. In addition to the problems associated with the clinical symptoms of these parasitic infections, it is important to stress the increase in cancer of the Gastro-Intestinal (GI) tract. In this study we evaluate the prevalence of cancer in patients affected by chronic inflammatory diseases caused by the above named parasites. In three years, from January 2000 to December 2003, we observed a total of 1199 subject. Of these, 950 presented with complaints of diarrhoea, vomiting, abdominal pain, melena, hematemesis, rectal discharges and alteration of bowel habits. A total of 818 patients were evaluated in Uganda (Mulago and Arua hospitals) and 381 at Luisa Guidotti Hospital in Zimbabwe. An exhaustive clinical history was collected for each patient and then physical and laboratory examinations were performed. The clinical files of all patients previously admitted to the respective hospitals were obtained and the information taken from these files was then integrated with our clinical findings. Subjects who were found free of gastro-intestinal disease after examinations and did not have a clinical history of infective GI disease but presented with other pathologies, were regarded as control group. The control group was composed of 249 subjects. The subjects who were positive on examination underwent further investigations. The number of patients affected by schistosomiasis and amebiasis were 221 and 224 respectively. The number of patients who suffered from aspecific enterocolitis was 454, intestinal tuberculosis was present in 21 patients and we found 30 patients with esophageal candidiasis. Patients who had the above mentioned GI diseases were then divided into 3 groups. First group was composed of patients who had a clinical history of infective GI diseases and were re-admitted for similar symptoms, and on examination were positive for the presence of the same infective GI diseases. Such patients were placed in the Chronic group. The second group was formed of patients who had previously undergone treatment for infective GI diseases but on readmission were found free of infective GI disease, and this group was described as the Cured group. They had symptoms associated with other pathologies. A third group, which we described as the Acute group was composed of patients who did not have any previous case of GI infection and were admitted for the first time. Such patients were found positive on examination for infective GI diseases. In the 950 patients, we found a total of 45 tumors. The tumors were prevalent (42 tumors) in the chronic group. In 34 patients the tumor was in the colo-rectal region, in 3 patients in the stomach, in 4 patients in the esophagus and 1 patient had cancer in the small bowel. Our results show a strong association between the chronic infection of the GI tract and the likelihood to develop tumors. However, it is not clear which biological mechanisms are implicated in such transformations. They may depend on the chronic inflammation of the GI mucous which permits the entrance of carcinogenic materials or on the effects of mutagenic products produced by the parasites or both.