The Computer Assisted Area Source Emissions procedure (CAASE) was used to allocate county total emissions to subcounty area source grid squares. The grid square system provided a continuous set of squares over the seven counties of the Twin Cities, Minnesota AQCR. Objective apportioning factors based on population, housing units, area of the grid square, or a combination of these characteristics were used for the distribution of most emission source categories. The application of these factors is included in the CAASE computer programs. The remaining emission source categories--diesel rail locomotive, aircraft operations, and waterborne vessels--were allocated on the basis of factors especially developed for this AQCR. The rationale used in this development is documented in this report. Assuming the correctness of the totals of each category of emissions furnished to the contractor, the allocated area source emissions should provide a suitable base for air quality modeling.