Background: Standardized patients (SPs) are frequently included in the clinical preparation of students in the health sciences. An acknowledged benefit of using SPs is the opportunity to provide a standardized method by which students can demonstrate and develop their competency. Relatively little is known, however, about the capacity of SPs to offer an accurate and standardized performance across a speech-language therapy student cohort. Aims: To investigate the accuracy, reproducibility (consistent performance of each SP across student interviews) and replicability (consistent performance of a number of SPs across each scenario) of SPs portraying three scenarios, each as a parent of a child presenting with a speech disorder. Methods & Procedures: Forty-four speech-language therapy students interviewed four SPs to gain a case history. All interviews were videotaped. The accuracy of SP portrayal of key features of each scenario was scored by an expert rater and two other raters. Data were analysed to determine levels of accuracy, reproducibility and replicability, and inter-rater reliability was evaluated. Outcomes & Results: SPs were found to have moderate to high levels of accuracy across the three scenarios. There were no significant differences in the performances of each individual SP across interviews or between all SPs on each scenario, indicating that reproducibility and replicability were achieved. Overall inter-rater reliability between raters across all scenarios was greater than 80%. Conclusions & Implications: The results would seem to indicate that SPs can present in a standardized manner within a speech-language therapy context, confirming the value of their inclusion in clinical education programmes. Suggestions for improving the training of SPs in order to maintain accuracy are highlighted.