Extrapolation methods for use in subcounty area planning are examined. Population projections are employed in the planning of many public and private programs and facilities. Three methods of making population projections are identified: extrapolations of past population trends, projections based on demographic rates (birth, death, and migration), and projections based on employment rates. Population, share, differential, and density extrapolation methods were used to simulate 10-year population projections for townships in Illinois and Indiana. Census data from 1930 to 1950 were used to project the 1960 population, and data from 1930 to 1960 were used to project the 1970 population. The data base consisted of 1,579 townships in Illinois and 198 townships in Indiana. Population extrapolation extends past trends of a township's population growth; share extrapolation extends past trends of a township's share of its county's population; differential extrapolation extends past trends of the difference between a township's growth rate and its county's growth rate; and density extrapolation projects a township's population density relative to a predetermined maximum density. Based on the findings of the study in Illinois and Indiana, it is concluded that a planning analyst can easily generate 50 or more projections for a township during a single working day. The accuracy of the extrapolation methods is discussed. Supporting data are tabulated.