efore the end of the 15th century, the city of Lille had half a dozen convents and numerous charitable foundations, most of which were located within the city limits. During the first third of the 17th century, the city expanded by about 50 hectares and the number of convents multiplied to counter the advance of the Reformation. Of these thirty or so convents, only three modern churches remain today (Carmelites, Discalced Carmelites and Jesuits). Three completely disappeared convents in Lille have been excavated and documented since the 1980s: the Urbanists, the Poor Clares, and the Dominican Sisters of the Abbiette. This poster proposes an overview of the documentation in the local collections (AD Nord, AM Lille, BM Lille, Palais des Beaux-Arts)3 likely to shed light on the subject. The departmental archives of the Nord are always the first to be consulted. The funds of the convents and hospitals of Lille (in series H, AH) are preserved there with varying fortunes and are profitably completed by the funds of the municipal archives. The latter, classified according to their own logic, essentially shed light on the relationship between the community studied and the aldermanic authorities: installation methods, adjoining buildings, extensions, transformations, etc. Revolutionary documents precisely establish the date of departure of the monks, and the inventories, which are often very precise, give a good picture of the organization and furnishings of a religious establishment at the end of the 18th century. Coupled with the deeds of sale reported in the registration funds and the cadastral matrices, these sources allow us to trace what happened to these vast plots of land in the dense and industrious city of the 19th century. The way in which the documentation was used obviously varied according to the means and time available for the study. The works of Canon Platelle and A. Lottin constitute the starting point for any investigation on the subject. The georeferencing, for the last ten years, of cadastral sheets, floor maps of the plan-relief ((The city of Lille has kept its plan-relief of 1745, but the hazards of its conservation mean that many religious establishments have frequently disappeared from the model. The recent restoration of the PBA’s relief plans has resulted in extensive photographic coverage, which we can access. The use of a GIS, which is fed by the layout of the enclosures, the location of the religious establishments, the parishes, etc., allows us to save time. Nevertheless, the examination of the archives and the partial transcription of selected sources, including the Memorials and the accounts, constitutes in our opinion an essential work to shed light on the vestiges brought to light during the diagnoses or the excavations and to propose a first prosopography of the religious, capable of informing the interpersonal links between the members of a given community, the town councillors and the urban patrician.