The Ras superfamily of small GTPases comprises a group of molecular switches that regulate an astonishing diversity of cellular functions. A deep understanding of mitogenesis, cytoskeletal organization, vesicle traffic, and nuclear transport now requires the inclusion of the small GTPases as essential components of the molecular machines that drive these processes. The rich complexity of the control mechanisms involved is evidenced by the recent discoveries of GTPase cascades, multiple downstream effectors, and interconnected networks of GTPase-regulated protein kinase cascades. The 1995 FASEB Summer Conference at Snowmass Village, Colorado, on the Ras GTPase superfamily provided testimony to the broad impact that the study of these proteins continues to exert on cell biology.