This study investigated the effect of two forms of intensive speech treatment, (a) respiration (R) and (b) voice and respiration (Lee Silverman Voice Treatment [LSVT]), on the speech and voice deficits associated with Idiopathic Parkinson disease. Forty-five subjects with Idiopathic Parkinson disease completed extensive pretreatment neurological, otolaryngologicai, neuropsychological, and speech assessments. All subjects completed 16 sessions of intensive speech treatment, 4 times a week for 1 month. Pre- and post-treatment measures included intensity and maximum duration during sustained vowel phonation. Intensity, habitual fundamental frequency, fundamental frequency variability, and utterance and pause duration were measured during reading of the “Rainbow Passage” and conversational monologue as well. Family and subject self-ratings were completed pre- and post-treatment for the perceptual variables loudness, monotonicity, hoarseness, overall intelligibility, and initiation of conversation. Significant pre- to post-treatment improvements were observed for more variables and were of greater magnitude for the subjects who received the voice and respiration treatment (LSVT). Only subjects who received the LSVT rated a significant decrease post-treatment on the impact of Parkinson disease on their communication. Correlations between descriptive prognostic variables (i.e., stage of disease, speech/voice severity rating, depression, and time since diagnosis) and magnitude of treatment-related change indicated these factors did not significantly predict treatment effectiveness. These findings suggest that intensive voice and respiration (LSVT) treatment, focusing on increased vocal fold adduction and respiration, is more effective than respiration (R) treatment alone for improving vocal intensity and decreasing the impact of Parkinson disease on communication.