Humans think and talk about regions and spatial relations imprecisely, in terms of vague concepts that are fuzzy or probabilistic (e.g., downtown, near). The functionality of geographic information systems wil! be increased if they can interpret vague queries. We discuss traditional and newer approaches to defining and modeling spatial queries. Most of the research on vague concepts in information systems has focussed on mathematical and computational implementation. To complement this, we discuss behavioral-science methods for determining the referents of vague spatial terms, particularly vague regions. We present a study of the empirical determination of downtown Santa Barbara. We conclude with a discussion of prospects and problems for integrating vague concepts into geographic information systems.