The maintenance of mountain pastures (called 'puertos' in Spanish) is doubly important because of their being a productive resource and their role in nature conservation. Their present use by transhumant livestock, the number of which has decreased by 40 per cent in recent decades, is studied. Mountain pastures typology according to physical and vegetation characteristics is related to the following socioeconomic variables: grazing intensity, the last price assessment and the trends in price evolution. Greater demand is due to the possibility of using cows instead of sheep, which, in its turn, influences in a loss in pasture value.