The Epidermal Differentiation Complex (EDC) is a co-ordinately regulated locus that is evolutionarily conserved within mammals. It consists of a large number of genes, organised into clusters of gene families, which mainly encode structural constituents of the cornified envelope which replaces the plasma membrane of fully differentiated keratinocytes. It is thought that the developmental program of gene expression at the locus is regulated by specific changes in chromatin structure (Williams et al., 2002). To investigate this, I have characterised the chromatin structure of the EDC in cultured cell lines. These include a keratinocyte cell line, HaCaT cells, in which the locus is active and control cell lines where the locus is inactive. Chromatin is structured on a number of different levels, by the covalent modification of nucleosomes, the arrangement of nucleosomes into chromatin fibres and the arrangement of chromatin fibres into higher order structures within the interphase nucleus. I have assayed chromatin structure on all these levels using Chromatin Immunoprecipitation and Sucrose Gradient Sedimentation Analysis of Chromatin Fibre structure, partnered with oligonucleotide microarrays and Fluorescent In-Situ Hybridisation. By doing so I have examined the role each level of chromatin structure plays in regulating the human EDC and, characterised the relationships between the different levels across a large co-ordinately regulated locus in the human genome.