Tissues are the product of gene expression programs involving orchestrated transcription of thousands of genes. Gene expression programs depend on recognition of specific promoter sequences by transcriptional regulatory proteins. How a collection of regulatory proteins associates with genes across a genome can be described as a transcriptional regulatory network. We have begun mapping the transcriptional regulatory network in human visceral organs by determining how HNF6, HNF1a, and HNF4a, transcriptional regulators critical for the proper regulation of liver and pancreatic transcription, associate with portions of 13,000 of the best characterized promoter regions across the human genome. Just as maps of metabolic networks describe the potential pathways that may be used by a cell to accomplish metabolic processes, a map of the transcriptional regulatory network describes potential pathways tissues can use to regulate global gene expression programs. We use the network of regulator-gene interactions to begin to describe liver and pancreatic regulatory network motifs. The incipient network map reveals that, as in S. cerevisiae, gene expression programs and cellular functions are highly connected through networks of transcriptional regulators that regulate other transcriptional regulators.