This Handbook on Promoting Women’s Participation in Political Parties aims at encouraging political party leaders, men and women alike, to support the integration of gender aspects into internal political party decision-making processes. It also seeks to develop the capacity of women politicians to advance their political careers. The key finding that has emerged during the development of this handbook is that internal party reform is critical to women’s advancement. A lack of internal party democracy and transparency, the absence of gender-sensitivity in candidate selection and outreach, as well as the failure to decentralize party decision-making processes, all inhibit women’s opportunities to advance as leaders within parties and as candidates for elected office. To this end, the handbook provides a valuable overview of voluntary measures that political parties can adopt to enhance gender equality within party structures, processes, policies and activities, as a means to provide both women and men equal opportunities to participate meaningfully in the political life of OSCE participating States.