Many recent social movements have been characterised by their commitment to direct democratic decision-making procedures and leaderless, non-hierarchic organizational structures. This political tendency also implies the search for autonomy from existing political institutions and practises. Movements seek instead to embody in the political action itself the social relations, ways of collective decision-making and values that are ultimately desired for the whole society. This prefigurative approach to social change is often criticized for being naiive or marginal. This thesis argues first that this is not the case, but that prefigurative politics is misunderstood due to its differing view on questions of strategy, organisation and ultimately the possibility of fundamental societal change. The dissertation first outlines the often implicit strategy or vision of change underpinning prefigurative politics. It then identifies as the key challenge for prefigurative movements their ability to avoid reproducing oppressive forms of power, ‘power-over.’ This understudied aspect is investigated through extensive ethnographic field research with the unemployed workers movement, MTD Lanús in Buenos Aires, and the Zapatista movement in Mexico. The thesis concludes that it seems impossible to completely avoid reproducing old forms of power. Often key individuals in the movements end up in a paradoxical position whereby, in an effort to ensure the group’s prefigurative nature, these individuals enjoy non-prefigurative influence. The findings imply that the state and corresponding political forms and practise are not the only source of hierarchic pressures. As such, it would be more useful to view prefigurative political action as desirable, yet impossible.