This study investigates how technical texts are revised. Ten professional translators were asked to revise an instruction manual that had been translated from French into German. The revised translations were evaluated by a subject-matter expert. The focus was on analysing (1) the sequence of operations performed by the participants to produce a German translation equivalent for a technical term left untranslated by the original translator, and (2) how the participants’ uncertainty manifested itself in the revision process. The results show that (1) operations performed to solve comprehension and expression problems often stop before relevant terminological knowledge has been acquired, and (2) available information is not always efficiently processed. These results suggest that a lack of pre-existing terminological knowledge undermines revisers’ overall feelings of certainty, preventing them from regarding the source text as an important source of knowledge acquisition and from establishing effective intratextual links. Suggestions for future directions include the study of how the different types of competencies and knowledge possessed by a reviser interact and how dictionaries are used.