The illegal and unsustainable wildlife trade (IUWT) poses a significant threat to the conservation of biodiversity. IUWT also finances violence, contributes to destabilizing national security, and hampers economic development in source countries. The trade in rhino horn is considered one of the most organized crimes and is fueled by growing demand in Asia. This has contributed to pushing remaining rhino populations to the brink of extinction. Whether a total trade ban or a tightly regulated trade would be the most effective means of regulation is heatedly debated. However, no study has explicitly examined consumers' preferences and trade-offs for these two options. Furthermore, despite the urgency of understanding the drivers of demand, the relative importance of the attributes of consumer's choice to purchase rhino horn remains unclear. The PhD research aims to examine these questions. The research follows a mixed-methods approach to build a detailed understanding of the determinants of demand for rhino horn in Vietnam in order to contribute to policy making and the informed design of behaviour change strategies to most effectively reduce demand. The research primarily focuses on: (i) the influence of different reference groups and campaign exposure effects on rhino horn demand, (ii) a critique of contemporary rhino horn demand reduction strategies, (iii) consumer preferences and trade-offs with respect to different attributes of their choice to buy rhino horn, and the price elasticities of their demand, (iv) socialpsychological determinants of the intention to buy rhino horn, and (v) new approaches to identifying and interviewing wealthy consumers about their illicit wildlife consumption. Both qualitative and quantitative methods are employed in this research, including literature review, in-depth and semistructured interviews, focus group discussions, surveys, and choice experiments. The research also combines the Theory of Planned Behaviour and the Theory of Interpersonal Behaviour to develop an integrative model for predicting the intention to buy rhino horn. Fieldwork to collect empirical data has been conducted in several periods, resulting in a dataset of more than 1,000 high-income wildlife consumers and six publications in international peer-reviewed journals.