There is extensive literature that indicates animals suffer considerably in the practices of factory farming and animal experimentation. In the light of the evidence of this suffering there is an urgent need to answer the question whether our current use of animals is ever morally justifiable. The aim of this thesis is to provide a critical examination of the moral status of animals and of our treatment of animals in these practices. My objective is to assess whether these practices are ever justifiable and whether we have a moral obligation to revise our attitudes towards our use of animals. Animals are often denied moral standing on the basis that they lack certain capacities, such as rationality, language and the ability to think. Further, it is often thought that animals' supposed lack of such capacities could be used as a defence for our use of them in intensive farming and animal experimentation. Thus, in examining the moral status of animals this thesis also examines animals and their capacities in order to determine whether any of the arguments given against the moral standing of animals are sound. In seeking to discover the extent of our moral obligations towards animals and the necessary conditions for moral standing, I will demonstrate that, although animals used in factory farming and experiments do have moral standing, the only consistent course is to extend moral standing to all living things. I will conclude that although the possession of certain much-prized capacities is not necessary for moral standing, many animals do indeed possess such capacities, including the ability to use language. Centrally this thesis calls for a re-evaluation of our attitudes towards animals, particularly in respect of our beliefs about animals used in factory farms and experiments.