This Manual is the first volume of a three-part series. It is directed at officials in central planning organizations, planning departments of relevant sectoral ministries and experts at central statistical offices. The manual presents the conceptual basis for integrating demographic variables in planning and provides detailed overviews of the cohort-component method of demographic projections and the headship rate method of household projections, introduces the techniques and discusses data requirements. Module One is related to the other two Modules of the series as well as to Manuals III and VIII.