The Montreal Protocol on substances that deplete the ozone layer was signed in Montreal, Canada, by over 150 countries at a convention in 1987 to cut the use of CFCs (chlorofluorocarbons). The aim of the Protocol was to protect the ozone layer in the stratosphere by decreasing and eventually eliminating the use of ozone-depleting substances like CFCs. It is regarded as one of the most successful international treaties in modern history.