A study was undertaken to evaluate existing methods of categorizing areas in buildings for pertinency to the requirements of federal agencies. The concern was primarily with defining classes of area within buildings, rather than allowances per individual, per machine, or other unit. Recommendations include--(1) adoption of a standard set of criteria, (2) comparisons between buildings should include nature of occupancy, intended functions, and site and location, (3) a data collection program should be instituted to provide information for the development of a rational method for evaluation and/or comparing building plans, and (4) a program should be instituted to establish a means of expressing the interrelationships among building areas on a realistic basis. The criteria for classifying, defining, and measuring building areas are given for--(1) gross area, (2) net assignable area, (3) custodial area, (4) circulation area, (5) mechanical area, and (6) construction area. A supplementary discussion includes the area classifications, evaluating building design, and future needs and action. (MM)