This book reports on a study which investigated (i) whether bilingual lexical access (BLA) is predicted by working memory capacity (WMC) and proficiency level in L2; (ii) whether WMC and L2 proficiency interact in predicting BLA, and (iii) the extent to which within-language competition affects BLA. 100 learners of English as a foreign language (L2) performed three WMC tests, two proficiency tests and one BLA test. Data analysis revealed that WMC and L2 proficiency both significantly predicted BLA. Higher spans retrieved lexical items faster than lower spans. Moreover, the facilitation effects of semantically related L2 distractors on BLA were shown to be an effect of task order. However, more proficient bilinguals obtained faster reaction times during the retrieval of L2 lexical items than less proficient ones, regardless of performing the control or the experimental condition first. Findings were explained mainly in respect to (i) the interplay between automatic and controlled processes in memory retrieval and their impact on the development of L2 proficiency, and (ii) the way lexical representations develop, are stored, retrieved and connected in a bilingual mental lexicon.