In this paper, we describe a qualitative user study of Searchling - an experimental visual interface that allows users to leverage a bilingual thesaurus for query formulation and enhancement. The design of Searchling is based on theories of thesaurus-based interface design from Shiri et al. , combined with the principles of rich-prospect browsing . The Searchling interface provides the user with three working spaces on one screen: the Thesaurus space, Query space, and Document space. We interviewed 15 graduate and faculty researchers at the University of Alberta, who carried out three structured tasks in a thinkaloud protocol, with simultaneous audio recording and screen capture. These participants identified a number of significant advantages to the researcher provided by Searchling, including the value of having an interface that could help with identifying search terms, suggesting preferred terms, and giving bilingual search support. They also suggested areas for future improvement, primarily related to our assumption that common knowledge of thesauri would be sufficient to make the various features clear if they were described using standard vocabulary from the thesaurus field.