Both human research and animal research operate within established standards and procedures. Although the human research environment has been criticized for its sometimes inefficient and imperfect process, reported abuses of human subjects in research served as the impetus for the establishment of the Nuremberg Code, Declaration of Helsinki, and the National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research and the resulting Belmont Report. No similar, comprehensive and principled effort has addressed the use of animals in research. Although published policies regarding animal research provide relevant regulatory guidance, these policies have not emerged from the process of specifying consistent and reasoned ethical principles. The lack of a fundamental effort to explore the ethical issues and principles regarding the use of animals in research has led to unclear and disparate policies. Recent studies have increased our understanding of animal cognition and emotion, suggesting that animals' potential for experiencing a wide variety of harms, such as pain and fear, is greater than has been previously appreciated. Furthermore, relationships between methods of captivity and certain laboratory procedures and the resulting adverse physical, social and psychological effects have been established. In light of this information, current protections may need to be reconsidered and modified. This paper explores the historical convergence and divergence in the creation of human and animal research guidelines, as well as opportunities to align ethical frameworks with new scientific discoveries.