Advanced learners' processing of linguistic knowledge in connection with a translation task from Danish into English is discussed. The focus of the discussion is on learners' use of different types of linguistic knowledge (the degree to which they use this linguistic knowledge and the form in which it is represented). The following issues are addressed: (1) introspection as an elicitation method in data collection; (2) a theoretical model based on cognitive psychology; (3) a taxonomy of three types of knowledge representation; (4) an analysis of learners' mental representations of linguistic knowledge along two dimensions. Pedagogical implications, particularly the role of grammar instruction, are also discussed. Analysis suggests that if the learner does not identify any particular problems in the translation process, solutions are arrived at based on skill- and rule-based knowledge. If the learner identifies problems, the solution pattern involves the application of knowledge or rule-based knowledge. The linguistically most competent learners are able to activate skill-based, or at most, rule-based knowledge. (Author/MSE)