Depending on the number of language versions required, the production of new language versions of patient-reported outcome measures (PROMs) will be costly in terms of both money and time. Health authorities have started to specify how PROMs should be adapted. The aim of the adaptation process is to achieve new language versions of PROMs that are conceptually equivalent to, and that meet the same psychometric and acceptability standards as, the original. Adaptation of an instrument into a new language involves four main stages: consideration of suitability for adaptation into target languages, translation into target language, assessment of acceptability to the new culture and establishing psychometric and scaling properties of the new language version. The adaptation of an instrument for use in another language highlights a number of linguistic, conceptual and technical issues. There are two main methods used in the adaptation of PROMs: forward-backward translation and dual-panel translation.