The Scottish National Party (SNP) articulates the demands of a nationalist movement whose antecedents stretch back at least to the beginning of the eighteenth century but which has aimed at secession only since World War I. Adopting as its strategy the election of MPs whose remit would be to sue for independence, the SNP remained electorally insignificant until the mid-1960s, since when it has won up to 30 per cent of the Scottish vote. This has had a considerable impact on the Labour Party, which now has a position on Scottish self-government that is much closer to that of the SNP than it has ever been before. As a party of the left, the SNP has an electoral base whose social characteristics appear, in some though not all respects, to be similar to those of Labour voters. Having suffered from considerable internal conflict during the first half of the 1980s, and from consequent electoral decline, the SNP is now on a rising trend. This may turn out to have unanticipated consequences for the British political system as a whole.