The purpose of this chapter is to overview the advances in the field of measuring and modeling the influence of geographic market potential and accessibility. In general the models are designed to assess the influence on location choices and growth performance. The initial question concerns the relationship between the two concepts ‘market potential’ and ‘accessibility’. Accessibility can be defined as the ability to reach goods, services, activities or destinations. Market potential can be described as the possibility of reaching customers, demand or some other resource. Both concepts have a long tradition in research. The concepts are often used to describe similar or even the same sort of phenomena. Evidently, we have two related concepts that essentially mean the same thing. Examples of this are illustrated by the following statements. ‘The concept of accessibility is not a new one, and has been introduced into regional economics and trade under the form of market potential’ (Behrens and Thisse, 2007, p. 462). The measure is ‘often called a potential accessibility index (sometimes simply called market potential), that measures accessibility’ (Yoshida and Diechmann, 2009, p. 3). In Combes et al. (2008, p. 304), the authors refer to Harris’s concept of market potential as ‘an indicator for the degree of accessibility to market’.