Interviews with UK manufacturing SMEs (small and medium enterprises) confirm, in aggregate, that traditional regulation drives environmental behaviour. Yet, beneath this aggregate picture, there are groups of firms that respond to regulation differently. Furthermore, within the aggregate and group levels there exist further differences across firms. SME responses can thus be understood as groups and subgroups of firms that at the same time are distinct. These identifiable differences result from firms' capacities and orientations, which are factors that determine receptiveness to regulation. The findings provide a more sophisticated account of SME behaviour than existed previously, and help us understand why and how regulatory measures may underperform. © 2013 © 2013 University of Newcastle upon Tyne.