Green parties are well established in many liberal democracies. The green party family is relatively homogeneous with parties sharing common ideologies, similar origins, party structures, and constituencies of support. Electoral performance is variablethere are around 15 established successful green parties but success elsewhere is limitedand shaped by various structural factors and country-specific political opportunities. Electoral success has brought new pressures on green parties to compromise their radical policies and practices. Green parties have joined or supported government coalitions involving parties of left and right, achieving some policy impact and demonstrating that they are responsible coalition partners.