This paper presents the TransSearch log-files. These are records of interactions between human translators and TransSearch, a bilingual concordancing system. The authors show how this data can be used as experimental evidence to study the translation process. This is exemplified by the results of a study on the nature of the text units on which human translators operate, based on this data. Finally, some enhancements to the TransSearch system are proposed, aiming both at improving its usefulness for the end-users and the quality of the data that can be collected from its log-files.