Actin filaments comprise an essential cytoskeletal array that organizes the cytoplasm during growth and cell division. In growing cells, actin filaments carry out many functions. Actin filaments position the endomembrane system and act as a substrate on which organelle motility occurs. Other actin-filament arrays appear to be more dynamic and to reorganize in response to growth signals and external cues. The diverse cellular functions of the actin cytoskeleton are mediated by actin-binding proteins that nucleate, destabilize, and bundle actin filaments. The distorted trichome morphology mutants provide a simple genetic system in which to study mechanisms of actin-dependent morphogenesis. Recent results from several groups indicate that 'distorted group' genes encode subunits of the actin-related protein (Arp)2/3 and WAVE complexes, and function in a cell morphogenesis pathway.