This thesis is concerned with the use of models in chemical education, in particular the way chemistry students use models in understanding chemistry. The study begins with an outline of the reasons for my interest in the subject of models in chemistry. The report describes some of the problems encountered by undergraduate chemistry students in dealing with three dimensional structures, and surveys literature relating to visualization skills in chemistry. Preliminary broad areas for investigation are identified including the relevance of models to students, problems of representing 3D structures, and students' use of models to solve chemical problems. A pilot study to gather information in these areas and to develop a suitable research instrument for investigation is described. The pilot study proved useful in highlighting errors in understanding chemical concepts, assessing practical model use, and considering students' perceptions of the relevance of models. This is followed by a consideration of the role of models in understanding chemistry in relation to the nature of model, chemistry and understanding, and the links and interactions between them. It discusses issues such as the match between the currently perceived roles of models in chemical practice and in chemistry teaching and the desirability of bringing these into line. It surveys the literature concerning purpose of model use in chemistry and describes the features of chemical structure models used in the research. Criteria for selecting appropriate data collection and analysis methods in a research study are considered and 80me of the methods adopted in recent chemical education research described. The chapter concludes with a description and justification of the particular research methods used in the study. The report gives details of the interviews carried out with selected scientists to consider the notion of 'the good chemist'. It then describes the videorecorded workshop interviews with forty five chemistry students relating to their appreciation and use of models in chemistry, and the follow up int.erviews with eight of the participants. Data from these interviews are analysed in an attempt to answer the research questions posed initially, including individual chemists' purposes in using models, patterns in model appreciation, perceptions of the good chemist, fiexibility of model use as an indicator of competence as a chemist, and the potential of the workshop interview in higher education assessment. The research findings are discussed in relation to existing literature, and the study concludes with a discussion of the implications for chemistry curricula, chemical education and for future research.