ABSTRACT The development of tourism in Mallorca has led to the island's economy being based, almost exclusively, on this sector. Since 1955 mass tourism has affected the economic and social structures of Mallorca. The development was based on a rapid growth of tourist demand and on a chaotic development of tourist facilities. This has had severe consequences for the island: insufficiently controlled urban planning, overcrowded beaches, and erosion of the beach-dune system caused by massive construction on the coastal zone. Many beaches have been transformed into urban beaches and their coastline has retreated. Solutions like sand renourishment have not stopped the erosion process. The increasing number of residents and visitors exerts a strong pressure over water resources producing overextraction and a lowering of the groundwater table in aquifers. A strong seasonal concentration of visitors in coastal summer resorts represents a high peak demand during the dry season. The exhaustion of groundwater resources and the higher water demand are managed with environmentally and economically expensive resources such as seawater desalination. The results show that the dwelling capacity of the island has been exceeded and the present levels of water demand and beach degradation are not sustainable. This indicates that tourism in Mallorca is becoming unsustainable and a water and coastal management policy is urgently required if sustainability is to be achieved.