The approach of `national styles of regulation' in comparative research of regulatory policy and expertise, stresses the importance of national traditions and institutions. Historically rooted institutions tend to be used to make sense of national differences. Although such national patterns can be identified and are corroborated by extensive empirical research, the conceptualisation runs into problems, especially when trying to understand policy change and in-country variation among policy sectors. Drawing on my own comparative empirical research on the regulation of environmental hazards of chemicals, I propose changes to the conceptualisation of national styles that accommodate variation among policy sectors. The structure of the science-policy boundary in expert advice is integrated as a crucial element for the description of variation in regulatory regimes.