Polycomb group (PcG) proteins are conserved epigenetic transcriptional regulators that maintain the transcriptional repression of silenced genes. giant (gt), a PcG target gene, is a zygotic gap gene involved in the development of the head and abdominal regions in Drosophila. We have generated a genetic system, triple mutant embryos (bcd osk tsl), in which maternal hunchback (Hb) is expressed ubiquitously but zygotic Hb expression is absent, resulting in the ubiquitous repression of gt by PcG proteins. Chromatin immunoprecipitation (ChIP) experiments on these embryos is being carried out at multiple developmental stages to determine the timing and locations of binding by transcription factors, PcG proteins, and deposition of histone modifications. We have initiated studies to (a) identify the roles of individual proteins in recruitment of PcG complexes and (b) determine the mechanisms by which PcG proteins distinguish between repressed and active target genes. Progress on these studies will be presented.