Purpose: Accurate measurement of speech intelligibility is essential for children with speech production deficits, but wide variability exists in the measures and protocols used. The current study sought to examine relationships among measures of speech intelligibility and the capacity of different measures to capture change over time. Method: Forty-five children with cerebral palsy (CP) with and without speech motor impairment were observed at ages 6, 7, and 8 years. The speech performance of each child was rated using four measures at each time point: standardized articulation test scores, multiword intelligibility scores obtained from naïve listeners, parent ratings of intelligibility, and percent intelligible utterances obtained from language transcripts. We analyzed the correlations of measures within each age and within three different severity groups, and we analyzed how these measures changed year over year in each severity group. Results: For children with CP who have mild and moderate speech deficits, different measures of speech production were weakly associated, and for children with CP with severe speech impairment, these measures showed stronger associations. The four measures also differed in their ability to capture change over time. Finally, results from standardized assessments of articulation were not found to inform overall speech intelligibility for children with mild and moderate speech deficits. Conclusions: Results suggest that speech production is not fully described by any single clinical measure. In order to adequately describe functional speaking abilities and to capture change over time, multiple levels of measurement are required.