The present article examines one property of bilingual speech – convergence – and strives towards explanatory depth by attending to the insights of the antecedent research in formal linguistics, psycholinguistics, and sociolinguistics. In particular, the paper adopts as a point of departure (and further substantiates) the argument that convergence will be evidenced in the syntax–pragmatic interface (Hulk and Müller, 2000) and the assertion that convergence is a ‘bilingual optimization strategy’ (Muysken, 2002), in advancing the claim that convergence (cum congruent lexicalization) in bilingual speech may be amplified or attenuated in tandem with the language mode (bilingual versus monolingual) of the bilingual (Grosjean, 1998). Specifically, it will be demonstrated through an analysis of two individual bilinguals' productions in both monolingual and bilingual modes that the convergence that is already manifested to some degree in these individuals' Spanish is enhanced in Spanish-English code-switching when their languages are simultaneously activated and deployed.