Trade area analysis has long been recognized as one of the fundamental prerequisites for successful marketing management. Not only is such analysis essential for effectively allocating firm resources, but it is vital as an initial step in understanding consumer behavior [18, pp. 128-9]. Thus, over the past 50 years numerous attempts have been made to provide an efficient method for defining and delineating trade areas. For example, in 1933 McGill [13] attempted to develop a suitable analytic method, and most marketers are familiar with the Law of Retail Gravitation [17], a pioneering effort to establish trade area boundaries mathematically, as well as the work in [1, 2, 4, 9]. Despite advances in trade area analysis, it still remains that the difficulty in developing yardsticks to measure trading areas has not yet been overcome [6, p. 283]. Therefore, the purpose of this article is to approach the problem of quantitatively defining and delineating trade areas from a slightly different perspective-that of trend surface mapping. In this manner, an objective, parsimonious map of consumer spatial behavior, unconstrained by unrealistic boundaries or assumptions, can be constructed. A second, closely related topic-that of examining and explaining any anomalies which may exist in a particular trade area-is also considered.