This thesis analyses the post-editing process by means of concurrent verbalisations. Four participants thought aloud while post-editing MT output produced by the METAL system. The need to investigate the postediting process, and the usefulness of the thinking-aloud technique to do so, are outlined in Chapter 1. By comparing the post-edited texts produced by the participants with the version generated by METAL, three major categories of syntactic change effected in the post-editing process were isolated. These were active-to-passive, noun-to-verb, and inter-TU changes. The execution of these changes was subsequently traced through the thinking-aloud protocols, and this forms the basis of Chapters 2, 3 and 4. Finally, Chapter 5 presents ensuing conclusions and recommendations.