Abstract : The objective of this doctoral thesis is to understand the modalities of supply of the home care service targeted at maintaining the care of elderly persons at home. Since the 1990s, the main evolutions of elderly care policies have led to favoring an industrial model of home care service typified by the intermediate organization for which a service provider acts as an intermediary between the elderly person and the care worker at home. The first part of this thesis shows that this modality of organization, in order to face up to the constraints, especially temporal ones, inherent in the care-taking of elderly persons, develops strategies of rationalization of time schedules (increased surveillance of the time spent for each activity) and job contracts (yearly calculation of working time). Hence, despite of the increased professionalism of the elderly care workers, the intermediary mode, contrary to direct employment between employer and employed, has not led to an improvement of the work conditions of the care workers. In parallel to the development of the intermediary mode, hybrid models of supply of home care, connecting the domestic model and the medical, social and industrial model, supported by a multitude of actors, nursing services at home, the team that evaluates the "dependent elderly allocation" etc. - have emerged. The second part of the thesis shows that the direct employment of a home care worker, mostly a cleaning lady, is a the origin of these mixed modes of organization. However, the latter have a varying form, just as the role of the care worker at home: the more or less important presence of the sanitary and social part depends on the degree of implication of potential helpers from the family, the level of dependence and the diversity of needs that are to satisfy to ensure the sustainability of home care. In these flexible modes of organization we show the emergence of putting in place an informal custodianship. It emerges to accompany the increase of workload linked to the growth of dependence, but reduces in addition the autonomy of dependent elderly persons.