In the previous chapter Martin Knapp and Jeremy Kendall reviewed a number of conceptual models which seek to define and classify voluntary organisations. In this chapter I shall attempt to tease out how voluntary organisations as a ‘sector’ function. I shall begin by discussing features of both the local and national voluntary sectors and will draw out some of the apparent tensions in the way voluntary organisations are responsive to their constituencies. I will then look at the role of the so-called intermediary bodies; consider briefly non-departmental public bodies; and then discuss the under-representation of certain sections of the population in voluntary action. Finally I will review a number of theoretical models which help our understanding of the voluntary sector as an industry.