The employment structure of The Netherlands and other advanced countries is evolving from industrial to postindustrial. Yet existing social class schemata, like the well-known Erikson, Goldthorpe and Portocarero (EGP) class schema, were constructed for an industrial employment structure. In this study, we adjust the EGP class schema to account for this transformation by using new class theories. We distinguish a ‘new’ class of social and cultural specialists and an ‘old’ class of technocrats with both a higher and a lower version in the service class. Our research question concerns the extent to which the adjusted EGP class schema is a better predictor of people’s political orientation than the standard EGP class schema. We assume that the ‘new’ classes differ in their political orientation from the ‘old’ classes. We also assume that, during their formation, the ‘new’ classes become increasingly effective in explaining differences in people’s political orientation. Experts’ knowledge is employed to classify the occupations. In addition, we use the data of 34,856 respondents gathered between 1970 and 2003 in The Netherlands. The adjusted EGP class schema explains people’s political orientation substantially better than the standard EGP class schema; the ‘new’ classes vote significantly more for leftist parties and differ substantially in their political orientation from the ‘old’ classes. Furthermore, our results show that the political orientation of the low-grade social and cultural specialists has become more crystallized since 1970.