During simultaneous interpreting, the interpreter relays a speech in a different language while the original speaker is still talking. The interpreter's job is to listen and understand the speech in the source language, analyse the information and then express it as precisely as possible in the target language. Given that this is an extremely complicated activity requiring maximum concentration, interpreters usually work in pairs and switch over every half hour to have a rest. It is also important to have two interpreters so that the interpreter who is not speaking can help their colleague by looking up terminology or informing the organisers if there is a problem.

Simultaneous interpretation takes place in specially-designed soundproof booths. The interpreters listen to the speaker through headphones and talk into a microphone at the same time. This is then transmitted to the audience. Participants using the interpretation service can listen to the interpreter via headphones while still watching the speaker.

During multilingual conferences several booths are provided, with interpreters for all of the necessary languages.