Numerous technical, cognitive, social, and organizational constraints and biases can reduce the quality of usability data, preventing optimal responses to a system’s usability deficiencies. Detecting and appropriately responding to a system’s usability deficiencies requires powerful collection methods and tools, skilled analysts, and successful interaction amongst usability specialists, developers, and other stakeholders in applying available resources to producing an improved system design. The detection of usability deficiencies is largely a matter of analyzing a system’s characteristics and observing its performance in use. Appropriate response involves the translation of collected data into usability problem descriptions, the production of potential design solutions, and the prioritization of these solutions to account for pressures orthogonal to usability improvements. These activities are constrained by the effectiveness and availability of methods, tools, and organizational support for user-centered design processes. The quality of data used to inform system design can, for example, be limited by a collection tool’s ability to record user and system performance, an end user’s ability to accurately recall past interactions with a system, an analyst’s ability to persuade developers to implement changes, and an organization’s commitment to devoting resources to user-centered design processes. The remainder of this article (a) briefly reviews basic usability concepts, (b) discusses common barriers to successfully collecting, analyzing, and reacting to usability data, and (c) suggests future trends in usability research.