This book is concerned with bilingual thematic dictionaries (BTDs). The three chief aims of the research project are: 1) to identify the characteristic features of the bilingual thematic dictionary, 2) to gauge its usefulness, and 3) to make suggestions as to how it could be improved. Various approaches are adopted in order to reveal the nature of the BTD. The typological approach considers the lexicographic genres (bilingual, thematic, and pedagogical) which have been combined to create this hybrid reference work. Particular attention is paid to the BTD's immediate forerunner and closest lexicographic relative: the monolingual thematic learner's dictionary. Detailed textual analyses of contemporary thematic dictionaries identify the characteristic features of the macrostructure, microstructure, and other components from a structural perspective. In order to evaluate the usefulness of the BTD features identified, the textual analyses are supplemented by three pieces of user research involving a questionnaire (to elicit learners' opinions), a test (on the effectiveness of the access structure), and an experiment (to discover how a learner uses a BTD).