This chapter looks at how scientists discovered the ozone problem and reduced uncertainty regarding the causes and effects of the depleting ozone layer. Against this backdrop, the study analyses how public authorities and the business community responded internationally to the challenge from the scientists. The analysis shows that the international effort under the Montreal Protocol was innovative in several ways, especially in the way developing countries were persuaded to join although the developed countries were mostly to blame in the first place. The result has been a sharp fall in the use and production of ozone-depleting substances.