Somatic gene therapy represents a new approach for treating a variety of genetic and acquired diseases and has many potential applications in gastroenterology. Somatic gene therapy is based on the ability to transfer recombinant genes efficiently into somatic tissues, such as the liver or intestine, and achieve expression of the recombinant gene product. Gene transfer could be used to replace genetically defective gene functions or prevent the progression of acquired or multifactorial diseases. The therapeutic application of gene transfer technologies requires development of methods for achieving efficient transfer and expression of recombinant gene products, research directed at developing strategies for altering the course of disease, and clinical research aimed at assessing both the technical feasibility and therapeutic efficacy of this approach.