Few studies were made on the intrinsic and co-intrinsic vowel characteristics in neurologic dysarthrias. This work evaluates these parameters in a group of 4 subjects with cerebellar dysarthria suffering from a cerebellar degenerative syndrome and a group of 4 subjects with Parkinson disease suffering from parkinsonian dysarthria. These subjects were compared with 10 control subjects. An intensive speech treatment inspired from the Lee Silverman voice treatment (LSVT) was applied to one of the parkinsonian subjects of the study, with assessment before and after rehabilitation. The acoustic measures assessed the duration and the frequency of the vowels [a, i, ul indifferent contexts as well as their formant frequency and sentence duration. The results show different impairments according to the type of the dysarthria, and some forms of contrast transposition. Speech therapy restores subnormal contrasts.