Using data from twenty industrialised countries, this paper presents a model attempting to explain the proportion of female representation in national legislatures. The results show the type of electoral system to be an important factor which can help or hinder an increase in women's political representation. While proportional representation systems facilitate the election of women, single constituency systems (such as Britain's ‘First Past The Post System’) constitute a major obstacle. The paper therefore argues that electoral reform in Britain is necessary if female representation in Parliament is to increase from the current 9% to parity within a reasonable time period.