This paper is the first attempt to analyse the relationship between unionisa ion, tempora y employment and non-s andard hours of work, compa ing Spain and Britain, which are character sed by relatively differen labou market stru ures and substantially different degrees of employment protections. Despite such differences, these two countries show similar responses of unionisation to flexible employment. In particular, we find tha union recognition in Britain and firm-level union presence in Spa n do not respond to changes in long hours of work and overtime hours, wherea temporary employment is negativ ly co elated with union cove ag in both ountries. We find, however, some differences between the two countries when the samples are stratified by industry.