In current research into second language (L2) speaking, aspects of fluency are measured as static constructs. Averaged over a complete speaking performance, for instance, syllables per minute is calculated. Similarly, the number of pauses is calculated per minute, averaged over a complete speaking task. This paper argues, however, that we need to investigate fluency as a dynamic construct. Research into L1 speaking has shown that L1 fluency aspects may show cyclical temporal patterns (Roberts & Kirsner, 2000). In addition, research into the changes in perception of L2 comprehensibility during task performance has shown that L2 comprehensibility may show dynamic patterns, with implications for ratings on comprehensibility (Nagle et al., 2019). This paper, therefore, argues that L2 fluency should be investigated as a dynamic construct as well. The paper finishes by sketching pedagogical implications and directions for future research.