Eleven middle school children were involved in designing interfaces for Web search engines. Children were given the role of “designers” of the interfaces rather than “reactionaries” to existing ones. Using a participatory approach, children created eleven paper prototypes for Web search engines based on their needs and knowledge structure and they transcribed the purposes of these interfaces. The prototypes were analyzed in relation to content-related spaces, specific spaces, general spaces, instruction spaces, and other spaces. Children’s comments about the purposes of the interfaces were analyzed in terms of functionality and visual design. This study describes the prototypes children created and highlights the need for designing Web search engine interfaces that provide high usability for children.