The Global Corruption Barometer is an opinion survey measuring the public's perception of corruption as well as the public's experience related to this phenomenon. The Barometer collects the public's opinions of the most corrupt elements of the public sector, and the most affected by corruption aspects of daily life (family, business, politics), as well as the action taken by the government to fight against corruption.

For each country included in the barometer, the respondents are chosen so as to be representative for the general public. The respondents are men and women over 15. Some of the respondent groups are national, others urban; the researchers make sure that all respondent groups meet the characteristics of the national and world population.

Gallup International polls public opinion on behalf of Transparency International, as part of the study "Voice of the People." The inclusion or exclusion from the Barometer of one country or another depends in principle on Gallup International and its network of associates, but in some countries the surveys are implemented by TI national branches or other organizations.