Abstract There has been much progress this year in characterizing the complex series of post-translational modifications important for GTP-binding protein function. In addition, the long-awaited molecular characterization of a G protein that regulates phospholipase C activity has been reported. Although the function of small GTP-binding proteins continues to be a puzzle, significant advances have been made in this area; in particular, many proteins affecting GTPase and nucleotide-exchange activities have been identified.