Learners make errors in both comprehension and production. Some theoreticians have pointed out the difficulty of assigning the cause of failures in comprehension to an inadequate knowledge of a particular syntactic feature of a misunderstood utterance. Indeed, an error can be defined as a deviation from the norms of the target language. In this investigation, based on personal and professional experience, a written composition entitled "My Life in Colombia" will be analyzed based on clinical elicitation (CE) research. CE involves getting the informant to produce data of any sort, for example, by means of a general interview or by asking the learner to write a composition. Some errors produced by a foreign language learner in her acquisition process will be analyzed, identifying the possible sources of these errors. Finally, four kinds of errors are classified: omission, addition, misinformation, and misordering.