The question of whether within chimera research certain human/nonhuman animal chimeras should not be created has received significant attention in the philosophical community. In this thesis I examine, from a philosophical perspective, four questions related to this topic. These are: (i) Can ‘human’ dignity be invoked as an argument against the creation of human/nonhuman animal chimeras? (ii) Is it morally permissible to kill human/great-ape chimeras in order to solve the human organ shortage crisis? (iii) Is there something inherently wrong with creating human/nonhuman animal chimeras capable of human gamete production and human pregnancy? (iv) Can classic animal ethics issues concerning animal welfare throw light on the issue of killing human/pig chimeras for their human organs. These four questions, in turn, fall within what have been regarded as the three main problematic cases within chimera ethics: (1) the creation of human/nonhuman animal chimeras that could have brains predominantly constituted by human brain cells; (2) the creation of human/nonhuman animal chimeras that could look human-like; (3) the creation of human/nonhuman animal chimeras capable of human gamete production and human pregnancy. In the introduction I do four things. First, I define what chimeras are and point out some problems with some of the definitions that have been proposed. Secondly, I briefly investigate if there is a sound principled objection against the intentional creation of all intraspecific and interspecific chimeras. Thirdly, I present in a detailed fashion the four questions that this thesis poses in response. Finally, I explain how the four papers that are the main body of the thesis form a coherent body of work. In the fifth section of this thesis I present the abstracts of four papers. In the sixth section I make a comprehensive exploration of the dignity-based arguments that have been advanced against the creation of human/nonhuman animal chimeras that could possess human-like mental capacities, or that could possess certain cognitive capacities that we would not be able to properly classify. In the seventh section I examine the morality of killing human/great ape chimeras for their human organs. This paper is a detailed response to Shaw et al.’s (2014) ‘Using Non-Human Primates to Benefit Humans: Research and Organ Transplantation’. The eight section covers two topics. First I discuss the moral problems related to the creation of mainly nonhuman human/nonhuman animal chimeras capable of human gamete production. Secondly, I discuss the moral problems that would be generated by the fact that a sentient nonperson human/nonhuman animal chimera, that is predominantly nonhuman, was pregnant with a human conceptus. In the ninth section I further examine the chimera welfare issues that have emerged from assessing the morality of using human/pig chimeras as human organ sources. In the conclusion of the thesis I present a summary of the main points I have explored, and proceed to present how my dissertation adds to the academic literature on chimera ethics. Finally, I present some areas for further research.