The problems associated with the international exchange of colour-television programmes are discussed. The interchange of programmes between Europe and America would be possible, without conversion between the scanning standards, if dual standards were adopted in Europe, and an experiment is described in which the feasibility of dual-standard colour television is assessed from the point of view of the subcarrier frequency-changing or translating process. It now seems certain that different colour systems, operating on a common 625-line scanning standard, will be used within Europe, and investigations have been carried out into methods of transcoding between the proposed systems. These investigations show that both translating and transcoding operations between one colour system and another on the same scanning standard can be accomplished without serious impairment of the picture quality.