E-commerce literature has rarely addressed the measurement of customer perceptions of web site service quality in digital marketing environments. It is argued that the current SERVQUAL and IS-SERVQUAL instruments need to be refined and validated to fit the digital marketing environment, as they are targeted primarily towards either traditional retailing or information systems contexts. This article validates and refines a comprehensive model and instrument for measuring customer perceived service quality of web sites that market digital products and services. After a discussion of the conceptualization and operationalization of the service quality construct, the procedure used in modifying items, collecting data, and validating a multiple-item scale is described. Subsequently, evidence of reliability and validity on the basis of analyzing data from a quota sample of 260 adult respondents is presented. Implications for practice and research are then explored. Finally, this chapter concludes by discussing limitations that could be addressed in future studies. The final EC-SERVQUAL instrument with good reliability and validity will be essential to the development and testing of e-business theories, and provide researchers with a common framework for explaining, justifying, and comparing difference across results.