The aim of this study is to analyse the steady—state portion of the first two formants (F1) and (F2) in the production of [CVp] sequences, containing vowels [i, a, u] pronounced in two speech rates (normal and fast), by groups of untreated and treated stutterers, and control subjects. Comparing data between the three groups of speakers, a reduction of vowel space is observed for stutterers at a normal speaking rate. When speech rate increases, no reduction of vowel space is noticeable, contrary to treated stutterers and controls.