The London Amendment was adopted in 1990 at the Second Meeting of the Parties to the Montreal Protocol held in London. The amendment introduced control measures for both production and consumption for three new groups of substances, namely other halogenated CFCs (Annex B, Group I substances), Carbon Tetrachloride (Annex B, Group II) and Methyl Chloroform or 1,1,1-trichloroethane (Annex B, Group III). Control measures also included restrictions on trade with non-Parties

The financial mechanism was also established (Article 10 of the Protocol) for providing financial and technical assistance to developing countries to enable their compliance with their obligations under the protocol. The financial mechanism meets the agreed incremental costs of developing countries in order to enable their compliance with the control measures of the Protocol.

The amendment further introduced HCFCs (Annex C, Group I substances), but only required reporting of production and consumption data for the Annex and did not introduce control measures for the Annex Group.

The London Amendment entered into force on 10 August 1992