Abstract Vocal jitter and shimmer measures of the fluent phonations of 14 stutterers, 12 male and two female, were compared with jitter and shimmer measures of a group of nonstutterers matched for age and sex. Each subject phonated four vowels nine times in random order. Each phonation was sustained for at least 5 sec and was tape-recorded. The mid-3-sec portion of each recorded vowel phonation was subjected to jitter and shimmer analyses. Measures for stutterers were larger in both instances. Significant differences between stutterers and nonstutterers were obtained for shimmer measures. Differences on jitter measures were not significant. High variability in the stuttering group accounted for the nonsignificant finding in jitter measures and, in general, indicated heterogeneity among the stutterers. Findings led to the tentative conclusion that in fluent sustained phonation, stutterers demonstrate less stable control of respiratory-laryngeal dynamics than nonstutterers.