The eukaryotic genome is packaged into a periodic nucleoprotein structure termed chromatin. The repeating unit of chromatin, the nucleosome, consists of DNA that is wound nearly two times around an octamer of histone proteins. To facilitate DNA‐directed processes in chromatin, it is often necessary to rearrange or to mobilize the nucleosomes. This remodeling of the nucleosomes is achieved by the action of chromatin‐remodeling complexes, which are a family of ATP‐dependent molecular machines. Chromatin‐remodeling factors share a related ATPase subunit and participate (...) in transcriptional regulation, DNA repair, homologous recombination and chromatin assembly. In this review, we provide an overview of chromatin‐remodeling enzymes and discuss two possible mechanisms by which these factors might act to reorganize nucleosome structure. BioEssays 25:1192–1200, 2003. © 2003 Wiley Periodicals, Inc. (shrink)