The article examines the effect of two factors on achievement test scores in English as a foreign language for specific purposes in higher education: preexisting linguistic competence and frequency of use of language learner strategies. The rationale for the analysis of language learner strategies as a factor affecting achievement test outcomes is outlined, and then language learner strategies and linguistic competence are defined. Results of international studies that have confirmed the correlation between these two variables are also presented. The results of this study indicate a statistically significant positive effect of general linguistic competence on achievement test scores. Among the constructs of language learner strategies, however, the only construct having a statistically significant effect on achievement test scores is metacognitive strategies. The article concludes with a discussion of findings and presentation of measures that could help students at lower levels of linguistic competence improve their achievement test scores. (Contains 2 figures and 9 tables.)