The purpose of this study was to develop a modified measurement instrument for service quality that includes human factor considerations. Tangibles, reliability, responsiveness, assurance, and empathy were dimensions commonly used to measure service quality through a survey instrument termed SERVQUAL. A sixth dimension, usability, was added in a modified survey instrument termed SERVUSE. To examine the predictive power of both instruments, 200 patients at an on-campus health clinic were surveyed. The survey measured subject expectations and perceptions regarding the service system. Gap scores were calculated as the difference between these two measures. Positive gap scores reflected the exceeding of customer expectations. Negative gap scores reflected a failure to meet these expectations. The three response variables were perceived quality, satisfaction, and behavioral intention. Usability was found to be a significant predictor of all response variables. It also adds significant predictive value to the regression models when measuring behavioral intention. C 2008 Wiley Periodicals, Inc.