Traditional explanations of interaction (trade) in city systems fail to capture the breadth and complexity of extraregional markets in the producer services. Building on market-process theory, which argues that markets are adaptive and rarely in equilibrium, the development of extraregional trade in the producer services was investigated as a form of firm-level entrepreneurship. While firms' entrepreneurial behaviors are influenced by a variety of internal characteristics, such as entrepreneurial spirit, size, age, and ownership, it is argued that a firm's location is an important conditioning factor on the degree of success it achieves with market expansion. The hypothesis is evaluated using spatial market extent data developed from a survey of 615 producer service firms located in 16 Midwest cities. A firm's degree of entrepreneurship is indexed by a qualitative assessment of its marketing activities, ranging from "aggressive" to "none." Cox proportional hazards models, in a spatialanalog of survival analysis, were used to examine the influence of entrepreneurship on the spatial extents of firms' markets. The results confirm that location, more so than firm size or age, has a significant influence on the spatial extent of a firm's extraregional trade. The influence of location is generally complex: surfacing directly as a market scale effect, and indirectly as a conditioning factor on the success of a firm's entrepreneurial behavior. The results suggest that extraregional trade in producers services is predicated on more than just production cost (i.e., internal or external scale economies) or distribution cost (i.e., distance) factors, and that behavioral theories of the market can provide meaningful insight into the geography of market interaction.