Previous research showing a bilingual advantage on a variety of executive control tasks has typically compared monolinguals and fluent bilinguals. No study to date, however, has examined whether these effects endure for bilingual individuals who revert to monolingualism (‘lapsed bilinguals’). We investigated this question by testing monolinguals, full bilinguals, and lapsed bilinguals on a flanker task and a working memory task. Fully fluent bilinguals exhibited significantly more accurate performance than monolinguals on the working memory task, with lapsed bilinguals performing between the other two groups. Thus, continued bilingual experience appears necessary to maintain these cognitive advantages at a high level.