In spite of the vast numbers of articles devoted to vocabulary acquisition in a foreign language, few studies address the contribution of lexical knowledge to spoken fluency. The present article begins with basic definitions of the temporal characteristics of oral fluency, summarizing L1 research over several decades, and then presents fluency findings from a corpus of oral productions in three different L2s. Investigation of disfluencies in the corpus (the distribution of long hesitations and two types of retracing) reveal the fundamental role of "lexical competence" in spoken fluency, which should, it is argued, be taken more thoroughly into account in our language-teaching programmes. (Contains 3 tables.)