Conventional wisdom suggests that parties are no longer as representative of their voters as they once were. It may also be the case that the problem worsens as parties lose members. This chapter tests the hypothesis that those parties with relatively low and/or falling memberships are less representative, both descriptively and substantively, than parties whose membership is relatively high and possibly even growing. It does this by drawing data from the Party Membership Project (PMP) and from the British Election Survey (BES) in order to compare members of six British political parties – some of which have recently enjoyed membership surges (Labour, the SNP and the Liberal Democrats), others of which have been less fortunate (the Conservatives, the Greens and UKIP) – with voters. It finds that, overall, women, the under-35s and ethnic minorities are underrepresented among members, whereas university graduates are clearly overrepresented, as are middle-class people and people living in the South of England and Scotland. However, although some parties are more representative of their voters than others, any relationship between size and growth, on the one hand, and both descriptive and substantive representativeness, on the other, is marginal, if it exists at all.