Housing needs is a concept of central importance to state and local planning in the United States (Landis and LeGates 2000). Roughly characterized as the number and type of housing units required to accommodate a population at a given standard of housing occupancy, the formulation of a quantified estimate of housing needs requires many assumptions that intertwine normative and empirical judgments. The overall aim of this article is to propose a needed theoretical framework and more rigorous methods for demographic component of housing needs estimates. Grounding this in the recent California experience helps to illustrate concepts with a concrete example. As demographic change continues to spread across the country, growing numbers of regions and cities can benefit from this study of the California experience. The article begins with a broad overview of the definition of housing needs, and then focuses on the central role of population growth and change in determining future construction needs. A pivotal issue is the instability over time of the empirical relationship between population and housing, as shown by comparison of household formation and homeownership rates from 1960 to 2000. A further issue is the sharp differences registered between different age groups, races, ethnicities, and nativity groups. Although disaggregation permits projections to capitalize on observed differences between groups, it also highlights the existence of inequities and the policy goal of reducing them.