Combinatorial transcription factor (TF) interactions control cellular phenotypes and therefore underpin stem cell formation, maintenance and differentiation. Here we report the genome-wide binding patterns and combinatorial interactions for 10 key regulators of blood stem/progenitor cells (Scl/Tal1, Lyl1, Lmo2, Gata2, Runx1, Meis1, Pu.1, Erg, Fli-1, Gfi1b) thus providing the most comprehensive TF dataset for any adult stem/progenitor cell type to date. Genome-wide computational analysis of complex binding patterns followed by functional validation revealed the following: First, a previously unrecognized combinatorial interaction between a heptad of TFs (Scl, Lyl1, Lmo2, Gata2, Runx1, Erg, Fli-1). Second, we implicate direct protein-protein interactions between four key regulators (Runx1, Gata2, Scl, Erg) in stabilising complex binding to DNA. Third, Runx1+/-::Gata2+/- compound heterozygous mice are not viable with severe haematopoietic defects at midgestation. Taken together, this study demonstrates the power of genome-wide analysis in generating novel functional insights into the transcriptional control of stem and progenitor cells. 10 Samples (9 Transcription Factors and 1 Histone Modification) and 1 Control (IgG). All from the same cell line, a haematopoietic progenitor cell line (HPC-7).