This article aims at reconsidering the concept of mobilization theoretically and with reference to contemporary political problems. For this purpose basic insights are drawn from the sociological classics. Mobilization is defined as the development of a social relationship (in Weber's sense of the word) between two types of actors, the individuals and the parties. The analytical concept of mobilization activities consists of three processes: the process of interest formation (cognitive dimension), the process of community building (affective dimension), and the process of employing means of action (instrumental dimension). Political mobilization is defined as the actors' attempt to influence the existing distribution of power. A directional variable is introduced in order to define more precisely the type of relationship which develops between individuals and parties. Three different models of vertical mobilization are then presented: two examples of models of downward mobilization, historical mobilization and the Leninist concept of the vanguard party; grass-roots or populist mobilization; and the ideal-democratic model of mobilization. A fourth model, horizontal mobilization, incorporates the possibility of internal processes of mobilization taking place within the two types of actors. These models help to analyse the present political situation as characterized by the coexistence of vertical and horizontal processes of mobilization, with an increasing predominance of the latter. It remains as a future task of mobilization research to investigate the assertion made here that the institutionalized hierarchical relationship between individuals and parties is weakening as a result of both actors' increasing orientation to themselves when becoming aware of and articulating interests, developing affective loyalties, and using means of mobilization.