Hundreds of different factors adorn the eukaryotic genome, binding to it in large number. These DNA binding factors (DBFs) include nucleosomes, transcription factors (TFs), and other proteins and protein complexes, such as the origin recognition complex (ORC). DBFs compete with one another for binding along the genome, yet many current models of genome binding do not consider different types of DBFs together simultaneously. Additionally, binding is a stochastic process that results in a continuum of binding probabilities at any position along the genome, but many current models tend to consider positions as being either binding sites or not. Here, we present a model that allows a multitude of DBFs, each at different concentrations, to compete with one another for binding sites along the genome. The result is an ''occupancy profile,'' a probabilistic description of the DNA occupancy of each factor at each position. We implement our model efficiently as the software package COMPETE. We demonstrate genome-wide and at specific loci how modeling nucleosome binding alters TF binding, and vice versa, and illustrate how factor concentration influences binding occupancy. Binding cooperativity between nearby TFs arises implicitly via mutual competition with nucleosomes. Our method applies not only to TFs, but also recapitulates known occupancy profiles of a well-studied replication origin with and without ORC binding. Importantly, the sequence preferences our model takes as input are derived from in vitro experiments. This ensures that the calculated occupancy profiles are the result of the forces of competition represented explicitly in our model and the inherent sequence affinities of the constituent DBFs.[Supplemental material is available online at http://www.genome.org. The COMPETE software is available at http:// www.cs.duke.edu/;amink/software/compete/.]Hundreds of different factors adorn the eukaryotic genome, binding to it in large number. These DNA binding factors (DBFs) are quite diverse. For example, nucleosomes occupy 75%-90% of the genome (Van Holde 1989), and DNA and RNA polymerases traverse large swaths of it at a time. In contrast, transcription factors and other specialized proteins and protein complexes-like the origin recognition complex (ORC)-bind to very specific regions of the genome, often only at specific times or under specific conditions. Key cellular processes involving the genomeincluding replication, transcription, and chromatin packagingare regulated by the spatio-temporal interactions of these various DBFs with DNA and with each other. Consequently, it is critical that we understand how these factors interact as they bind to the genome.In particular, DBFs bind to the genome in competition with one another, jockeying for position along the DNA. As one example, to fit into the nucleus, DNA is highly compacted into chromatin in a hierarchy of levels. The lowest level is the formation of nucleosomes, where ;150 base pairs of DNA are coiled around a histone octomer. Since transcription factors (...