Questionnaire translation is a crucial aspect when it comes to collecting comparable survey data in different countries or among different language groups. In the widest sense, translation should ensure the implementation of 'equivalent' instruments, in different linguistic, cultural and institutional settings.

The quest for equivalence already starts at the questionnaire development stage, in which advance translation can already contribute to a more 'translatable' source questionnaire. It continues in the translation stage through procedures - such as using multiple translators with varying skills and providing them with extensive information and task specification. In the review or assessment stage, committee assessments have been argued to contribute to questionnaire equivalence, more so than the use of 'back translation' which was common practice in many multi-lingual surveys in the past. Pretesting and documentation should round off all these translation procedures (e.g., Harkness 2003).