When policymakers and practitioners decide that "empowerment" - usually of women or the poor - is a development goal what do they mean? And how do they determine the extent to which it has been achieved? Despite empowerment having become a widely used term in this context there is no accepted method for measuring and tracking changes. Presumably if we want to see people empowered we consider them to be currently dis-empowered i.e. disadvantaged by the way power relations presently shape their choices, opportunities and well-being. If this is what we mean then we would benefit from being better informed about the debates which have shaped and refined the concept of power and its operation. Many sociologists, political scientists and anthropologists have discussed power but little of this debate appears to have percolated into development studies. Therefore in this paper I briefly review how the concept of power was debated and refined during the second half of the twentieth century and discuss how power relations might be described and evaluated in a particular context. I then consider how the empowerment of women has been discussed within development studies and make some suggestions as to how it might be assessed.