Abstract : The ambulatory with radiating chapels has always been considered as a sign of ostentation and modernity for the chevets of romanesque churches. It may be defined as an aisle circumscribing the central point of a church's chancel and is generally associated with the notion of pilgrims circulating around particularly important relics. The very early examples of this type of chevet (from the 10th to the first half of the 11th century) are concentrated in the provinces of the middle Loire and show imperfectly accomplished features. Four collegiate churches were selected in order to develop an approach through the archaeological analysis of the standing buildings : Saint Aignan of Orléans, of which the chevet was built in the image of that of the cathedral of Clermont-Ferrand, Saint Martin of Tours, Notre-Dame of Mehun-sur-Yèvre and the Madeleine church of Châteaudun. The perspectives offered by these studies show deep changes brought about in the building techniques through the use of regular ashlar masonry. The structural role of the ambulatory in supporting the apse should be taken into consideration when trying to understand the development of this architecture, be it for the widespread use of vaulting or the search for better lighting. In the absence of material proof, the functional interpretation of a corridor designed for pilgrims must be rejected. The relations between the people who financed these buildings show that the novelty of their construction served as a statement of royal prestige, directly orchestrated by Robert the Pious and his followers.