Discussion of new forms of party organisation have largely focused on the ways in which institutionalised parties have adapted to pressures towards ‘catch-all’ or ‘electoralprofessional’ behaviour. This article examines the ways in which new parties respond to these pressures. A model of the ‘party as business firm’ is generated from rational choice assumptions and it is suggested that such a model can emerge when new party systems are created in advanced societies. Two cases of political parties which resemble the business firm model in important ways are analysed in order to gauge the consequences of this type of party organisation: UCD in Spain and Forza Italia in Italy. On the basis of this analysis it is argued that business firm parti...