A field experiment provided the first test of the hypothesis that intergroup attitudes within a nation predict the group members' attitudes toward the break-up of the nation. Prior to a referendum on the devolution of power from Britain to Wales, Welsh (minority) and English (majority) participants indicated their attitudes towards each other and towards devolution. As expected, there were significant correlations between intergroup attitudes and attitudes towards devolution, and these relations were different for Welsh vs. English participants. English respondents who held more positive attitudes towards Welsh people were significantly more favourable toward devolution, whereas Welsh respondents who held more positive attitudes towards English people were significantly less favourable towards devolution. A subsequent laboratory experiment provided a conceptual replication of this result, using manipulations of majority vs. minority status and of intergroup attitudes towards potentially devolving groups in psychology. These findings demonstrate that intergroup attitudes are highly relevant to understanding attitudes regarding devolution.