In the central centuries of the Middle Ages, the development of cities and with them a significant population engaged in non-agrarian activities was made possible by agricultural growth and the supply of the countryside to the city. However, the demographic increase of the cities made it necessary, in order to ensure their food supply, to extend their influence and even their domination over vast agricultural areas both nearby and further afield. Irrespective of the role that subsistence production may have continued to play in these regions, the need to feed the cities led to the widespread extension of production for the market, i.e. a mercantile orientation of agricultural production that determined the crops to be sown and cultivated as well as a progressive integration of the agricultural prices. The session will address the measures taken by the various municipal governments in late medieval Iberia (Catalonia, Majorca, Valencia, Andalusia, Castile and Portugal) to ensure their food supply and even their food sovereignty. Measures aimed at favouring imports while prohibiting exports, at buying large quantities of food in nearby regions in competition with other cities, and even at fighting for it. But there were also measures taken by individual urban landowners who ensured their food supply by buying up agricultural property or imposing rents in kind rather than in money. This also had important repercussions in the countryside, where monoculture of cash crops spread and a stratum of wealthy peasants emerged and consolidated as a result of the commercialisation of agricultural production.