In the current paper we investigate the relation between secular cycles and millennial trends. The tests we have performed suggest that the structure of millennial trends cannot be adequately understood without secular cycles being taken into consideration. At a certain level of analysis millennial trends turn out to be a virtual byproduct of the demographic cycle mechanisms, which turn out to incorporate certain trend-creating mechanisms. Demographic-political cycle models can serve as a basis for the development and testing of models accounting not only for cycles but also for secular trends. In order to do this, we suggest to alter the basic assumptions of the earlier generations of demographic cycle models (that both the carrying capacity of land and the polity size are constant). The variables such as carrying capacity of land, cultural complexity, and empire sizes are actually not constant, but rather experience long-term trend dynamics in the rise, and the new generation of models needs to account for this fact.