The present papers intends to be a review study of lexical transfer. This overview does not claim to be exhaustive, but a review of some of the main variables influencing the process of cross-linguistic influence in lexis. The factors addressed in the present paper are i) L2 proficiency, ii) L1 background, iii) gender, iv) motivation, and v) learning context. In general terms, as learners' L2 proficiency increases the influence of the L1 decreases. Learners whose L1 is typologically related to the TL tend to resort more frequently to their L1 for lexical transfer purposes, but learners from different linguistic backgrounds seem to undergo the same lexical transfer processes. Studies investigating the interaction between gender and lexical transfer and between more and less motivated learners seem to reveal lack of differences. Finally, there exist quantitative and qualitative differences in L1 lexical transfer of CLIL and non-CLIL learners in their written compositions.