This chapter reviews the ethical structure underlying clinical testing. It describes the chronological development of this field, with the crucial milestones—the Nuremberg Code, the Declaration of Helsinki, and the Belmont Report—all of which recognize three basic principles: respect for persons, beneficence, and justice. These formative documents are required to protect participant rights and to maintain public trust in research. The chapter underlines informed consent, confidentiality, and privacy as being critically important, while it also mentions historical violations of ethics as a justification for rigorous oversight in research practices. It also looks at various regulatory frameworks, such as ICH GCP, guidelines by CIOMS, WHO standards, and roles of national regulatory authorities like FDA, EMA, and CDSCO. It discusses the complexities regarding informed consent, especially in vulnerable populations, ethical dilemmas around placebo use, and randomization of trials. It also addresses new trial designs, issues related to data privacy and post-trial obligations, with an emphasis on participant welfare and scientific integrity as imperatives. The modern-day challenges also include the use of artificial intelligence and patient-centric approaches, which raise very pertinent questions related to algorithmic bias and engagement of participants. Ethics committees and CABs are highlighted for their contributions toward culturally sensitive research practices. In the end, this chapter recommends continuous education in ethics and the elaboration of unified ethical standards internationally, while compliance with established guidelines is vital for participant protection and responsible medical knowledge acquisition.