We examined 16 cases of gastrointestinal cancer, of which 11 were from the colon, 1 from the rectum, and 4 of gastric origin, cytogenetically for expression and for loss of heterozygosity (LOH) on chromosome 18 using Deleted Colon Cancer (DCC) gene. LOH on chromosome 18 with DCC probe was detected in 7 out of 11 cases of colon, in 4 out of 4 cases of gastric and in 1 case of rectum cancer. In all gastrointestinal tumors the expression of DCC gene was absent, while it was present in normal tissue. We also found rearrangements of chromosomes 18 (10 cases) and 17 (9 cases), leading respectively to deletions of long and short arms. Other additional abnormalities were observed involving chromosomes 5, 6, 15 and 19. The data recorded in our series differ from other authors' data in three respects: a high incidence of pseudodiploid chromosome number, rearrangements of chromosome 19 and 15, and involvement of DCC gene in the development of gastric cancer, as well as in colorectal cancer as previously reported.