In this paper we examine the connection between union membership and economic inequality. Using several surveys from the International Social Survey Programme (ISSP) covering the period 1985-2002, we initially examine the impact of relative earnings position on union membership and show that union membership is concentrated in the intermediate earnings groups. Next, we examine the impact of inequality attitudes on union membership. We show that union membership is not only affected by individual expected benefits related to education or earnings, but that attitudes towards inequality also play an important role. When controlling for attitudes, however, the relative income position remains significant in affecting the probability of union membership. We also show that there are no significant trends in the relationship between relative income positions and union membership. Our results indicate that union decline is observed in face of increasing earning dispersion, by attracting fewer members at both tails of earnings distribution.