This article describes how political parties in parliamentary election campaigns in Western Europe make use of negative campaigning and examines whether their behaviour differs from that of candidates competing in US presidential election campaigns. Furthermore, it theorises how the differences and similarities between negative campaigning in these countries can be explained. First of all, this comparative study adds to the development of a more general theory on negative campaigning. Second, the study presents interesting new data measuring the use of negative campaigning by 31 political parties in 23 parliamentary election campaigns in Germany, the United Kingdom and the Netherlands between 1980 and 2006. Results show that there are no signs of an increase in negative campaigning and that the majority of attacks are issue attacks. However, there are systematic differences in the overall level of negative campaigning between these countries and we suspect that the type of party system could be the main explanatory factor.