Reporter gene analysis of two regions of the human factor VII (FVII) gene promoter (residues -658 to -1 and -348 to -1, where +1 is the start site of translation) in the mammalian liver-derived cell line HepG2 showed reduced transcriptional activity in the presence of oestrogenic factors. This effect was independent of promoter polymorphic haplotype. Similar analysis using a smaller region of the promoter spanning residues -187 to -1 failed to show any evidence of oestrogenic suppression. Electrophoretic mobility shift assays and supershift assays using recombinant oestrogen receptor alpha and anti-oestrogen receptor antibody localized the sequence motif to which oestrogen receptor was binding to residues -225 to -212 of the FVII promoter. The lack of oestrogenic suppression in a reporter gene construct spanning residues -658 to -1 modified to abolish oestrogen receptor binding at this site, confirmed the functional significance of this motif. Although superficially similar to the classical oestrogen response element (ORE), comprising two half sites separated by three spacer nucleotides, the FVII ORE represents an alternative type of ORE in which the two half sites are separated by just two spacer nucleotides. EMSAs indicated that increasing spacer nucleotide number from two to three in the FVII ORE, or decreasing it from three to two in a consensus ORE sequence motif, had a small effect on the binding affinity for oestrogen receptor. These data correlate with and provide a plausible mechanism for the inverse relationship between FVII and oestradiol levels observed during the menstrual cycle.