The essence of stuttering lies in its changeability, disfluency of speech appears and disappears in some communication situations, sometimes forever. Most often the cause of stuttering is said to be located in the central nervous system, but this does not mean that another hypothesis claiming that it is located in the autonomic nervous system is wrong. A theory of stuttering which does not explain this phenomenon is not particularly helpful. The difference of stutterers’ cardiovascular system activity is the only one noticed so far by the authors, but the structure of c.v.s. function changes is not clear. The goal of our study was to asses c.v.s. activity during speaking in detail. 13 stuttering and 17 non-stuttering volunteers underwent 3 different 5-minute verbal tests, preceded by a 10-minute resting period with continuous heart rate and blood pressure monitoring. No substantial variations in the cycle of changes in the activity of the cardiovascular system was noticed during the anticipation of speech and while speaking in stutterers and non-stutterers. A slightly steeper shape of the parametric curve in stutterers may suggest that they are less immune to communication stress, and that only their autonomic nervous systems are more labil. The cardiovascular system activity first decreases, increases directly before speech, and slows down during speaking; the reactions did not depend significantly on fluent or disfluent speaking. Our study sample did not prove the autonomic stuttering theory, but suggests that other experimental trials should be conducted to differentiate the reasons of c.v.s. lability.