Studies on Controlled Language (CL) suggest that by removing features that are known to be problematic for MT (termed here “negative translatability indicators”, or “NTIs”), the MT output can be improved. It is assumed that an improvement in the output will result in lower post-editing effort. This study tests that assumption by measuring the technical, temporal and cognitive post-editing effort (Krings 2001) for English sentences in a user manual that have been translated into German using an MT system and that have been subsequently postedited by nine professional translators. The post-editing effort for sentences containing known NTIs is compared with the post-editing effort for sentences where all known NTIs have been removed In addition, relative post-editing effort (Krings 2001) - a comparison of post-editing effort and translation effort - is also measured. The methodologies employed include the keyboard monitoring tool, Translog, and Choice Network Analysis Results indicate that temporal and technical effort is greater for those sentences that contain known NTIs. Other findings are that some NTIs result in higher post-editing effort than others and that post-editing effort can also be expended for sentences where NTIs have been removed.