Conventional kinesin and myosin are founding members of two distinct superfamilies of proteins responsible for motility. While members of both protein families generate force and are responsible for producing motion, they show no detectable sequence homology, despite the fact that their three-dimensional structures are clearly related. We have determined the homologous regions of the two proteins by structural comparison. This has revealed a conserved structural architecture shared with other ATPases, and has revealed residues conserved between kinesin and myosin. We are currently examining these residues to understand their function. We are also comparing the conserved structural regions to other motors, in particular dynein, and also searching for novel members of this fold family by searching sequence databases.