It has become apparent recently that a variety of small GTPases (small GTP-binding proteins or smgs), related to the oncogene ras, are involved in many cellular functions, especially membrane traffic and cytoskeleton regulation. This review will summarize some of the major themes that are emerging, focusing on the presence and possible functions of these smgs in the gastrointestinal tract. In addition, new cellular locations and functions for heterotri-meric G-proteins, previously believed to be solely associated with plasma membrane receptors, are becoming evident and will be discussed here.