Abstract Utterance fluency is widely acknowledged to be three-dimensional (i.e., speed, breakdown and repair), but little direct evidence has been offered in support of its dimensionality. This study examines the factor structures of speed and breakdown fluency and their relationships with EFL proficiency by evaluating 162 EFL learners’ retelling performances with respect to commonly used speed measures as well as pause length and frequency measures. Findings from structural equation modeling show that speed fluency was represented by articulation rate and mean length of utterance, and breakdown fluency by mid-clause pause length and frequency as well as end-of-clause pause length. Although speed and breakdown fluency were strongly related, EFL proficiency had a direct effect on speed fluency but not on breakdown fluency. When articulation rate was replaced with speech rate as the sole measure of speed fluency, the factor structure of breakdown fluency was changed and EFL proficiency contributed a little more to speed fluency. These findings help to better understand how EFL learners make pauses and how measures of speed and breakdown fluency differ from but simultaneously relate to each other.