Oregon's land-use planning program is often cited as an exemplary approach to forest and farmland conservation, but analyses of its effectiveness are limited. This article examines Oregon's land-use planning program using detailed spatial data describing building densities in western Oregon. An empirical model describes changes in building densities on forest and agricultural lands from 1974 to 1994, as a function of a gravity index of land's commuting distance to cities of various sizes, topographic characteristics, and zoning adopted under Oregon's land-use planning program. The effectiveness of Oregon's land-use planning program is evaluated based on the statistical significance of zoning variables and by computing estimated areas of forest and agricultural lands falling into undeveloped, low-density developed, and developed building density categories, with and without land-use zoning in effect. Results suggest that Oregon's land-use planning program has provided a measurable degree of protection to forest and agricultural lands since its implementation.