This monograph reviews research on the design and evaluation of search user interfaces that has been published within the past 10 years. Our primary goal is to integrate state-of-the-art research in the areas of information seeking behavior, information retrieval, and human-computer interaction on the topic of search interface. Specifically, this monograph (1) describes the history and background of the development of the search interface; (2) introduces information search behavior models that help conceptualize users’ information needs, and how people seek, select, and use information; (3) characterizes the major components of search interfaces that support different subprocesses based on Marchonini’s information seeking process model; (4) reviews the design of search interfaces for different user groups, especially that of vulnerable people, as well as personalized and adaptive search interfaces; (5) identifies evaluation methods of search interfaces and how they were implemented in research having different evaluation purposes. We also provide an outlook on the future trends of search interfaces including conversational search interfaces, search interfaces supporting serendipity and creativity, and searching in immersive and virtual reality environments.