Experimental support can be found in the literature for the hypothesis that increased variability in the motor part of the speech production system directly contributes to speech dysfluency. This hypothesis was tested once again in the present investigation by comparing the fluent speech of the two groups of stutterers and a control group of nonstutterers during the repeated production of a test sentence. One of the stuttering groups never achieved full fluency while the other did. Durational variability was descriptively greater for the stutterers than for the nonstutterers. However, variability did not significantly differentiate stutterers who could, with practice, produce the test sentence fluently in ten successive trials from those who could not. The latter result is contradictory to the prediction that results from the variability hypothesis. It suggests that the increased variability in speech-related variables found in the speech of those who stutter result from some other mechanism. Such a mechanism may be incomplete acquisition in childhood of the strategies necessary for the adult speech motor control. Educational Objectives: The reader will learn about and be able to describe (1) the variability that characterizes the normal speech production process, (2) the hypothesized relationship between durational variability in fluent speech and stuttering, and (3) how such variability is hypothesized to result in dysfluent speech.