This chapter presents the Central Business Index (CBI) method of central business district (CBD) delimitation. The technique requires a distinction between central business uses and land uses that are not central business in character though often found in downtown areas. The really essential central business activities appear to be the retailing of goods and services and the performing of various financial and office functions. An exception to the general rule regarding the non-central business classification of manufacturing is made in the case of a city newspaper. When the purpose of the land-use mapping is merely to delimit the CBD, it is sufficient simply to divide all the land use into central business uses and non-central business uses. The third-or upper-floors map is a generalized representation of utilization at the third and higher floors. Above the second floor, use is normally so uniform that such a generalization is practicable.