The Fourth International Conference on Bacterial Locomotion and Signal Transduction (BLAST IV) will be held January 9-13, 1997, in Cuernavaca, Mexico. The conference, which is expected to have 200-250 participants, will focus on the molecular mechanisms of sensing and movement in simple bacterial systems. The meeting format is designed to foster extensive discussions of recent developments and ideas among researchers from the United States and abroad. Approximately 60 oral presentations and 150 posters will be included in the program, allowing virtually all laboratories working in this rapidly moving field to present their key findings. Scientific sessions will compare and contrast the sensory and locomotor systems of a variety of prokaryotes, focusing on each fundamental step in their signal transduction pathways: (a) transmembrane signaling by chemo- and photo-receptors; (b) signal transduction by intracellular phosphorelay cascades; (c) sensory control of cellular motility and gene expression; and (d) the mechanics of cell motility. In previous years the meeting has provided an important forum for emerging concepts and generalizations concerning bacterial sensing and motility, and has presented the first molecular details concerning the structure and function of a family of signaling proteins that are pervasive in prokaryotic organisms and are now turning up in eukaryotic cells as well.