Using the massively parallel technique of sequencing by oligonucleotide ligation and detection (SOLiD; Applied Biosystems), we have assessed the in vivo positions of more than 44 million putative nucleosome cores in the multicellular genetic model organism Caenorhabditis elegans. These analyses provide a global view of the chromatin architecture of a multicellular animal at extremely high density and resolution. While we observe some degree of reproducible positioning throughout the genome in our mixed stage population of animals, we note that the major chromatin feature in the worm is a diversity of allowed nucleosome positions at the vast majority of individual loci. While absolute positioning of nucleosomes can vary substantially, relative positioning of nucleosomes (in a repeated array structure likely to be maintained at least in part by steric constraints) appears to be a significant property of chromatin structure. The high density of nucleosomal reads enabled a substantial extension of previous analysis describing the usage of individual oligonucleotide sequences along the span of the nucleosome core and linker. We release this data set, via the UCSC Genome Browser, as a resource for the high-resolution analysis of chromatin conformation and DNA accessibility at individual loci within the C. elegans genome.[Supplemental material is available online at www.genome.org. SOLiD raw sequencing data from this study have been submitted to the Short Read Archive at NCBI under accession no. SRA001023.]The regulation of genetic information within eukaryotic cells involves a high degree of specificity both in the availability of individual DNA-binding factors in individual cells, and in availability in the genome of DNA sequences that are their potential targets. Modulating the accessibility of individual DNA sequences are many complex interactions, the most prevalent of which are the interactions between histone octamers and DNA in compacted chromosomes. Each histone core interacts with 147 bp of DNA, which coil 1.7 times around the histone octamer (Luger et al. 1997;Davey et al. 2002) to form the basic unit of chromatin structure, the nucleosome. Since the first description over three decades ago (Kornberg 1974), the nucleosome and its role in gene regulation has been the subject of intensive study and speculation.As we have an increasingly detailed functional view of the genome, the tools of high-throughput molecular characterization have been used to begin obtaining a genome-wide description of nucleosome positions (Satchwell et al. 1986;Yuan et al. 2005;Johnson et al. 2006;Albert et al. 2007;Lee et al. 2007;Peckham et al. 2007;Schones et al. 2008;Shivaswamy et al. 2008). These data have in turn been used in attempts to reveal nucleosome positioning signals in DNA sequence (Satchwell et al. 1986;Ioshikhes et al. 1996;Segal et al. 2006;Yuan and Liu 2008). Although of great interest and value, sequence-based predictions of nucleosome position have been limited to date in their accuracy and resolution.In the litera...