Carcinomas of the upper gastrointestinal tract have been intensively studied for decades in order to identify markers for a) design of simple blood tests to detect presence or recurrence of the disease, b) prediction of therapy response, c) identification of molecular targets for novel therapies. These aims have not yet been fully reached by analysing single genes. However, some genes, including E-cadherin that is altered in sporadic and familial cases of gastric cancer and interleukin 1-beta whose polymorphisms together with Helicobacter pylori infection are associated with an increased risk for gastric cancer, may have the potential for clinical use. In this review we summarize current data for the single gene approach and provide an overview for recent results from cDNA microarray studies.