Purpose: This study investigated the validity of real-time measurement of percent syllables stuttered (%SS), and whether slowing down the rate of presentation of recorded speech samples, or independent measurement of the number of stutters and the number of syllables improved this validity. Method: Eight speech-language pathologists (SLPs) measured %SS from 16×3-minute audio samples of stuttered speech, presented in the following ways: (1) concurrently counting stutters and syllables at original speed, (2) concurrently counting stutters and syllables with the speed of presentation slowed by about a third, (3) independently counting stutters and syllables at original speed, or (4) independently counting stutters and syllables at reduced speed. All measures were compared with previously determined 'expert consensus' values. SLPs also rated each method for ease of use. Results: Results showed no significant difference between the expert consensus measures and any of the measurement methods in terms of validity or reliability, despite SLPs generally finding the modified methods easier to use. Conclusions: Neither slowing down the rate of presentation nor counting stutters and syllables independently improved the validity or reliability of real-time measurement of %SS by SLPs.