The first zygotic genes to be expressed during early Drosophila development are the gap genes. Their role is to read and interpret coarse positional information deposited in the egg by the mother and to refine it by cross-regulatory interactions and by controlling a class of pair-rule genes. Little is known about the molecular mechanisms by which the three cloned gap genes carry out their genetically defined functions. Here we report that the Krüppel (Kr) gene product (Kr) binds to the sequence AAGGGGTTAA, whereas the hunchback (hb) gene product (Hb) recognizes the consensus ACNCAAAAAANTA. We have identified binding sites for these proteins upstream of the two hb promoters, which we suggest could mediate the repression of hb by Kr and perhaps allow hb to influence its own expression.