The high occurrence of speech symptoms, most notably reduced loudness, in individuals with Parkinson disease (PD) implicates the respiratory speech subsystem as a factor in speech disorders associated with PD. In the current study, respiratory kinematics were used to assess the function and variability of the respiratory subsystem during speech in six individuals with PD as compared to three normal age-matched controls. Individuals with PD were found to have a greater reliance on the abdomen for changing lung volume than control subjects. Further, individuals with PD had more variable respiratory movements than control subjects, and this variability increased when the individuals with PD were externally cued (by the researchers) to speak louder. Although individual data reflected various patterns of change in respiratory function accompanying increases in sound pressure level (SPL) following the Lee Silverman Voice Treatment (LSVT), these patterns were not consistent or significant for group data. All individuals with PD increased SPL when they were externally cued to be louder and post-LSVT. However, the amount of SPL increase and the strategies used for increasing SPL varied both within and across subjects. For four of the six individuals with PD, mechanisms for increasing SPL were different in the external cueing condition as compared to post-LSVT.