This chapter is an overview of the study of lexical cross-linguistic influence (CLI) in oral production at different stages of third language development. The character of CLI in the developing vocabulary is illustrated with data from learners of French and Italian as foreign languages in Sweden. Different types of formal vs. meaning-based CLI are displayed and discussed in relation to the proficiency level of background languages and target language. Linking research into CLI to more general views on vocabulary learning, the study shows that CLI in L3 production is predominantly formal in early stages of development and that meaning based CLI shows in later stages. New data that confirm results from earlier studies pointing in this direction are presented.