Over the past year, the thrust of work in the field of heterotrimeric G proteins has been primarily in the following areas: first, resolution of their three-dimensional structures by X-ray crystallography; second, elucidation of the effect of lipid modifications on the Gα and Gγ subunits, third, understanding the role of the Gβγ dimer in stimulation of a variety of effectors following receptor activation; and fourth, identification of the points of contact among the Gα, Gβ, and Gγ subunits, and between these subunits and their cognate receptor or effector molecules.