The concept of exploitation is central in social and political theory, but there is no precise, widely accepted definition. This paper analyses John Roemer’s seminal theory, which construes exploitation as a distributive injustice arising from asset inequalities, with no reference to notions of power or dominance. Firstly, an intertemporal generalisation of Roemer’s static economies is set up and several doubts are raised on the claim that exploitation theory can be reduced to a kind of resource egalitarianism. Then, Roemer’s philosophical arguments that exploitation should be defined as a merely distributive concept are also questioned and it is argued that a notion of power, or dominance, is an essential part of the definition of exploitation.