Taking a broad historical perspective, this article analyses the development of the Swedish class structure. During the last decades, Sweden experienced a relative decrease in its middle class and a stronger polarisation of its class structure. Three potential factors can explain this development: changes in labour market behaviour, a reduction of the extent of decommodification of the Swedish welfare state and large structural changes in employment and occupational structure. We show that the long-term tendency towards an upgrading of occupational structure in Sweden has benefitted the upper middle class and the top-income group. Indeed, the large investment in research and development, the expansion of education and the increase in the demand of high-skilled jobs have limited the tendency towards job polarisation found in liberal market-orientated welfare states. Weakly linked to the modifications in the skill structure, the decrease of the middle class appears to be better explained by the postponement of entry into the labour market related to the expansion of education and by social protection reforms that negatively affected the disposable income of vulnerable groups.