In the Spanish Pyrenees sheep farming systems have traditionally involved an inverse or descending transhumance. In these less favoured areas, farming systems play a relevant role in the protection of the environment. The farming systems practised are conditioned by several factors, amongst them the environment and the family situation in the farms. The present paper analyses the different ways of organizing transhumance and its relation to the socio-economic characteristics of the family. By means of a multivariate analysis, three types of transhumance systems were obtained from a sample of 25 farms. The farmer's age, the continuity of the farm, the number of family members working on the farm, pluriactivity and the number of pensions are studied in every group.