In this Special Issue, we finally included 20 papers, focused on multiple clinical diseases, including cancers, infectious diseases (COVID-19, pancreatitis, etc.), autoimmune diseases, and metabolic diseases. In terms of the types of biomarkers, they include non-coding RNA, inflammatory factors, cytokines, etc. These papers have explored the clinical biomarkers in diagnosis, risk stratification, treatment response, and prognosis assessment in their respective fields, which is of great significance for the clinical management and future research pertaining to these diseases.