This paper has sought to examine the validity of contrastive analysis by researching the predictability of errors in the language production of a second language English speaker. To achieve this goal, the linguistic differences between English, and the test subject’s first language, Swedish, were examined. Following this venture, predictions were made about possible negative transfer in our subject’s language production.Predictions were based on the idiosyncratic phonological, syntactic, morphological, and lexical characteristics of Swedish. To test these predictions, four interviews were given over the course of several months in an attempt to confirm or disconfirm these predictions. The subject’s language production was isolated as a txt. file for corpus analysis. Word frequencies and contextual language usage were analyzed and discussed at length. Based on the accuracy of pre-interview predictions, it was concluded that contrastive analysis may be a modestly effective tool for making general inferences about possible interlanguage episodes and language learner difficulties.