The population of monk seals Monachus monachus on the Desertas Islands started to decline dramatically after the 1970s, hence the introduction of a project for the conservation of the species in 1988. Since then measures have been taken to achieve effective protection of those islands, and environemental education, monitoring and research programmes have been carried out. Methodologies used have been as non-intrusive as possible. Ten years later, the results have proved to be very positive. The monk seal, as well as its habitat, are adequately protected and the population, estimated at 20 individuals, is now on the increase with the growing number of births. With regard to the finding of biological and ecological data on the species, although somehow limited, it has been sufficient to help establish the most suitable strategies for the protection and conservation of the monk seal on the Desertas Islands.Resume. -La population de phoques moines, Monachus monachus, des lies Desertas a regresse de fagon accentuee ä partir des annees 70. C'est pour cette raison qu'en 1988, un programme pour la conservation de cette espece a debute. Depuis lors, des actions de protection effective de ces iles, des actions d'education environnementale, de suivi et de recherche ont ete realisees. Les methodologies utilisees sont autant que possible non intrusives. Dix ans plus tard, on a pu constater que les resultats etaient tres positifs. Le phoque moine et son habitat sont proteges de maniere adequate et la population, estimee a 20 individus, se trouve en phase de recuperation. On constate egalement une augmentation de la production annuelle de jeunes. Quant ä la determination des parametres de la biologic et de l'ecologie de cette espece, bien que limitee, eile permet neanmoins de definir les strategies les plus adequates ä la protection et a la conservation du phoque moine dans les lies Desertas.