Purpose: To provide preliminary evidence of the construct validity of the Communicative Effectiveness Survey (CES) for individuals with dysarthria and idiopathic Parkinson's disease (PD). Method: In a prospective, quasi-experimental design, 25 participants each were assigned to 3 groups (N = 75): PD and dysarthria, non-PD and no dysarthria, and PD significant others (SOs). Mean CES ratings were used to test for significant differences between the PD and non-PD group, and PD and SO rating of PD's communicative effectiveness. Multiple linear regression tested for significant predictors of CES ratings for PD group only using sentence intelligibility and spontaneous speech intelligibility scores as predictor variables. Results: The PD group rated their CES significantly lower than did the non-PD group. The PD group rated their CES significantly higher than their SOs rated them. Neither speech intelligibility score was a significant predictor of CES ratings. In follow-up analysis, the Hoehn and Yahr PD staging accounted for 47% of the variability in CES ratings for the PD group participants. Conclusions: This study provides preliminary evidence of the CES's construct validity. Clinicians and researchers who assess and treat individuals with PD may consider adding an additional assessment to the traditional clinical measures (i.e., speech intelligibility) by obtaining a measure of communicative effectiveness. (Contains 5 tables and 1 figure.)