Recent advances in three areas of myosin research--structural biology, in vitro motility assays, and mutagenesis--are leading to a new understanding of the molecular mechanism of chemomechanical transduction by this motor protein. Highlights include rational design of mutants using the crystal structure of subfragment 1, combined in vivo and in vitro mutant analyses using Dictyostelium, and the emergence of baculovirus as an in vitro system for expression of mutated mammalian myosins.