Web administration of measures offers numerous advantages as well as some drawbacks; the efficiency of collecting data in this way is dramatic. An important by-product of Web administration of measures is the option of creating paradata that offer information about how respondents access a measure (server-side paradata) and navigate within the online environment (client-side paradata) to complete the measure. Paradata can play a critical role in developing and piloting measures as well as refining the measurement process. Uses of paradata in Web-administered measures include (1) informing the choice of response formats, (2) examining the extent of changing response options, (3) examining the extent of following a prescribed sequence in completing a measure, (4) tracking the response process, (5) aiding in designing a Web-administered measure and its layout, and (6) assisting in determining the most appropriate log-in procedure. Because of the potential value of this new type of useful data to researchers in nursing and health, this article focuses on paradata within the context of Web-administered measures. More specifically, the article focuses on the definition, generation, and uses of paradata, as well as the ethical issues and other concerns in obtaining and using paradata. Uses of paradata to test the usability of information systems used in nursing and health practices are also included.