MIS literature has not addressed the measurement of customer information satisfaction in electronic commerce. Current models for measuring user information satisfaction (UIS) and end-user computing satisfaction (EUCS) are perceived as inapplicable as they are targeted primarily towards either conventional data processing or the end-user computing environment. This study develops a comprehensive model and instrument for measuring customer information satisfaction (CIS) for web sites that market digital products and services. This paper first discusses the concepts and definitions of customer information satisfaction from the literature. We summarize our findings in a theoretical framework. Based on this framework, we develop a measurement instrument to measure customer information satisfaction. The procedures used in generating items, collecting data, and purifying a multiple-item scale are described. We have carefully examined evidences of reliability, content validity, criterion-related validity, convergent validity, discriminant validity, and nomological validity by analyzing data from a quota sample of 520 adult respondents. The norms of the instrument are then developed, and the potential applications for practitioners and researchers are explored. Finally, we conclude this study by discussing limitations and potential future research. We hope that our CIS instrument can be used by other researchers to develop and test Internet marketing and EC theories in the future.