This introductory article provides a short account of the theoretical framework and the methodological set-up of a comparative study of street demonstrations. The following articles in this issue report results from this study. The data on over 90 street demonstrations and more than 17,000 participants were collected between November 2009 and Summer 2012 in nine different countries: Belgium, Czech Republic, Italy, Mexico, the Netherlands, Spain, Sweden, Switzerland and the UK. This introductory article presents the focal theme of the project – the impact of contextual variation on mobilization dynamics, the composition of the crowd and the demonstrators’ motives. The various contextual layers we are distinguishing are discussed. Following the theoretical framework the methodological set-up is presented. Identical measures and procedures are employed in all individual protest surveys. This introduction discusses the sampling procedures; but as each article concerns a different set of measures, the selection employed is discussed in the individual articles. The introduction concludes with an overview of the articles included.