Psychometrically qualified usability evaluation instruments offer many advantages to the usability practitioner. Advantages include objectivity, replicability, quantification, economy, communication, and scientific generalization. It is important that instruments used in usability evaluation have shown acceptable estimates of reliability, validity, adaptability and practicality. This paper compares the psychometric properties of the Post-Study System Usability Questionnaire (PSSUQ) instrument in Lewis’ study to a recent study that tailored the PSSUQ instrument to measure the user satisfaction of the usability of a webbased health provider interface. Lewis reported that the PSSUQ had acceptable psychometric properties. However, Lewis’ stated PSSUQ had limited generalizability and needed further examination. This research validated the PSSUQ instrument using a larger sample size in a different domain. The factor analysis and the clustering of the sub-scale items were different than Lewis’ results. Nevertheless, this research concluded that the PSSUQ instrument is adaptable and produced solid psychometric results.