The promoter of the mouse albumin gene contains at least six binding sites for specific DNA-binding proteins (A to F). Four of these sites (A, D, E, and F) can be occupied by transcription factors that are considerably enriched in liver nuclei, as compared to spleen or brain nuclei. These factors consist of a heat-stable protein that fills sites A, D, and F, and a member of a family of nuclear factor I (NF-I) related proteins that occupies site E. Site C binds a protein that is equally abundant in liver, brain, and spleen nuclei. Occupancy of this site and the binding of the heat-stable factor to the immediately adjacent site D appear to be mutually exclusive. However, both of these competing binding sites are required for maximal in vitro transcription.