The article is based on the author’s research project, started in 1983. The aim of this corpus-based project is to reconstruct mental translation procedures. Translation procedures, which underlie translation performance, operate in the translation process and are therefore not directly observable. In the first project phase the translation processes of advanced language learners are studied. The results are described in the author’s monograph Translation Performance, Translation Processes and Translation Strategies (1991). The second phase started in 1990 and studies translation process of professional translators. The third phase, in which translations of bilingual children are analysed, is being prepared.