A comprehensive analysis of the organization of the major political parties of France, Spain, Italy and Greece. Conceived and framed with a common theoretical approach, four national teams of researchers followed a structural approach to the study of party organization, and they have underlined the various characteristics of the parties. The party analyses are not limited, however, to the measures of party organization - number of members, local branches, elected officials, or to formal rules. Rather, the chapters highlight the power relationships among the various actors, leaders and factions.