This paper uses campaign contribution data to examine trade policy preferences among political action committees. With perfect factor mobility, as the Heckscher-Ohlin (HO) model assumes, interest group trade positions should depend on their factor of production but not on their industry. We show, consistent with the 2 × 2 HO model, that capital groups consistently back representatives supporting trade liberalization while labor groups favor protectionists. Unlike previous work, we also measure the variation in trade policy preferences within capital and labor groups. We find evidence that the industry net export position significantly affects labor unions' trade policy preferences. Industry characteristics have no impact on capital group lobbying. The former result suggests that empirical analyses of labor PAC contributions that exclude industry characteristics may be misspecified. Copyright Blackwell Publishing Ltd 2004.