This research focuses on collective behavior, examining the conditions under which groups of individuals engage in protests, riots, and other forms of contentious action in order to identify characteristic patterns and common elements of such actions. The study has three principal objectives. The first is to analyze how and why these patterns of collective behavior change over time. The second is to determine why the involvement of various types of individuals in collective actions changes, with different groups engaged at different points in time. The third objective is to assess the effects of various forms of collective action on the interests of the individuals involved. These questions are addressed in a broad historical context, attending to the implications for collective action of changes in the national state and the economy. Dr. Tilly focuses specifically on collective action occurring in London during the last half of the 18th century and in Great Britain generally during the early part of the 19th century. The 1828 to 1834 period is of particular interest, since this was a time of political turmoil and reform that set the stage for the rest of the century. The years preceding 1828-1834 are also sampled to establish a basis for assessing changes up to this period. Dr. Tilly will draw his data from newspaper accounts of contentious gatherings and use multiple regression, event history and network analytic techniques to analyze the data, with individual gatherings as the units of analysis. The theory and findings of this study, though historically anchored, bear equally on major questions being asked regarding contemporary forms of collective action. The analysis of the role of the state and the economy in fostering or thwarting such behavior may be especially revealing in gaining a deeper understanding of the conditions and events precipitating collective action.