Early development of the Drosophila embryo is under the control of some maternal genes responsible for the establishment of its general pattern. Three sets of genes determine the anteroposterior pattern; two distinct systems specify anterior and posterior development and a third one, the terminal system, is responsible for the development of the poles of the embryo. A different set of genes specifies dorsoventral polarity, which is established by the graded activity of the dorsal gene product. Here I analyze the effect of the terminal system on the expression of two zygotic genes involved in dorsoventral pattern, snail and decapentaplegic, and I show that this effect is mediated by a reduction on dorsal activity by the terminal system. Due to the interaction of these two systems, both of which use transmembrane signalling mechanisms, the poles adopt a more dorsalized fate than their counterparts in the middle of the embryo.