The process of clinical diagnosis is the cornerstone of modern medical practice. In this chapter, it will be shown that in order to facilitate accurate and timely diagnoses, clinicians must take into consideration evidence, ethics, and justice. This in turn means that best diagnostic practice demands that we be pluralists about evidence, that we recognize that in the process of clinical diagnosis ethical considerations are inextricably intertwined with evidential ones, and that diagnostic decisions regarding whom to test and when must be made on a case-by-case basis, while taking into account individual patient concerns. Finally, the chapter will also illustrate that when considering issues of health justice, the clinician must be primarily concerned with his or her individual patient, and only secondarily with societal considerations.