Do hospital services, like other services and commerce, contribute to the structuring of geographical regions, as proposed by central place theory? This question raises the issue of the rating of hospital facilities in land use planning policies. According to the theory, a polarized region forms around a central place due to the minimization of transport costs by consumers seeking to satisfy their needs. If a center offers more central functions (rare trades, services for individuals and businesses), its level in the urban hierarchy is raised and its area of influence expands. This theory was validated using a model, the variant of the gravitation model proposed by Huff. Brazil is an excellent testing ground for these hypotheses due to the great variety of geographic situations, economic and social development levels and the availability of sufficient data. Geographic research has resulted in the construction of an urban center hierarchy based on central functions, and the Unified Health System (or SUS) systematically records authorizations for hospital admission (or AIH) throughout the country. Processing of the 12 million AIH for 1996 showed that in a quarter of cases, the individual was admitted to hospital in a town other than their town of residence (exogenous AIH). Mapping the percentage of exogenous AIH makes it possible to delimit the area of influence of health services (observed influence) for the whole of Brazil. In Minas Gerais State, these areas of influence were compared with the estimates made according to the Huff model (calculated influence), with adjustment for distance and the number of hospital beds. Differences between the observed and calculated areas of influence are due to factors not taken into account by the model, such as the heterogeneity of many regions in the country. However, the accuracy of the estimation is satisfying, as is the simplicity of the equations. All the results tend towards a single conclusion: hospital services play a major role in the structuring of geographic space, by increasing the attraction potential of urban centers.