Many local governments are adopting inclusionary zoning (IZ) as a means of producing affordable housing without direct public subsidies. In this paper, panel data on IZ in the San Francisco metropolitan area and suburban Boston are used to analyse how much affordable housing the programmes produce and how IZ affects the prices and production of market-rate housing. The amount of affordable housing produced under IZ has been modest and depends primarily on how long IZ has been in place. Results from suburban Boston suggest that IZ has contributed to increased housing prices and lower rates of production during periods of regional house price appreciation. In the San Francisco area, IZ also appears to increase housing prices in times of regional price appreciation, but to decrease prices during cooler regional markets. There is no evidence of a statistically significant effect of IZ on new housing development in the Bay Area.