Human and animal mobility—especially ruminants for the latter—is a key factor in the Sahelian region. Animals are kept mobile to look for better grazing areas and water resources, to be sold at international markets and to escape insecure areas. The demographic growth of the western African coastal countries (and northern Africa for eastern Sahel) is changing the mobility pattern in the area. Old and new problems are faced by pastoralists and traders. As it is, mobility is a complex phenomenon. Here we describe livestock mobility in the region, showing some of the benefits and challenges that it faces nowadays. In West Africa, mobility is a complex phenomenon. It involves different spatial (from few kilometres to international journeys) and temporal (movements can take few days till several months) scales and it is contributing to local and regional economy in different ways: through livestock trades and the creation of jobs around the commercial circuits. Amajor issue is the scarcity of available data. In the absence of a centralised system, volumes of traded animal are mostly guessed: quantitative information is rarely available. A clearer and more quantitative knowledge of the livestock mobility network could greatly help veterinary officers to improve control and surveillance of animal diseases. In this chapter, we focus on the movements of cattle and small ruminants.