Ten individuals with Parkinson disease (PD) and hypokinetic dysarthria were compared with age-matched neurologically normal (NN) speakers on acoustic measures from speaking and vowel phonation tasks as well as on perceptual ratings of connected speech. Listeners identified differences between the groups when asked to judge the severity of vocal and articulatory impairment during reading. Several conventional acoustic measures failed to differentiate speakers with PD from NN speakers. However, measures of the shape (statistical moments) of the long term average spectrum (LTAS) revealed statistically significant differences between the groups across vowel phonation, reading and monologue tasks. The ease of computation of these spectral moments makes them appealing in clinical research.