Many policymakers concerned about high housing costs argue that easing development through altered land-use regulations can increase building, thereby boosting affordability and reducing segregation. I develop a framework to explain links—sometimes contradictory—between upzonings and construction, prices, and demographics. I evaluate scholarship and compare findings with research on downzonings impeding development. Evidence indicates that upzonings offer mixed success in terms of housing production, reduced costs, and social integration in impacted neighborhoods; outcomes depend on market demand, local context, housing types, and timing. Research on regional upzoning impacts is nascent but outcomes appear positive. Downzonings limit construction and worsen affordability.