Excerpts from the Introduction: The Cropland Availability Component of the National Interregional Agricultural Projections (NIRAP) system projects changes in the cropland base. Additions to cropland include conversion of pasture and range and forest land, including development of irrigated cropland, while losses of cropland include urban expansion, highway construction, airport construction, reservoir development, surface mining, recreation and wildlife reserves, vacation home developments, and loss of irrigated cropland. A critical review of the component by this author identified two major types of revisions needed. The more important was and still is the inclusion of economic variables in the component. The variables would explain cropland increases and decreases by the economic conditions both on and off the farm. To do this a model of farm level decisions would be used and would likely include opportunity costs of cropland. Ultimately the revision would link the Cropland Availability Component with the Land Use Component of NIRAP. Even though some work has been done on the linkage this revision is viewed as long range. A more immediate revision involved improvement of some of the sections of the present component. This revision was essentially one of updating the land data base with information from research and surveys completed and data made available since 1969 the most recent year of the data in the component prior to revision. This working paper is the product of that activity. This working paper is a replacement for some of the documentation of the component: it includes a new section on the calculation of the cropland base, a section on increase in non-irrigated cropland, and one on the cropland reduction resulting from urbanization section.