Biomarkers which are used for clinical purposes are known as clinical biomarkers. Clinical biomarkers provide a active and influential way to understanding the scope of many diseases and epidemiology, random clinical trials, screening for drugs or disease diagnosis and prognosis. It is defined as changes in the constituents of cells or body fluids, these clinical biomarkers offer the means for standardized classification of a disease and risk factors, and that can extend the basic information about the underlying pathogenesis of diseases. The main researches in clinical biomarkers are done in the fields of drug discovery. pharmacogenomics, oncology, and disease diagnostics. Classes of Biomarkers in Clinical trails are Safety biomarkers & Efficacy biomarkers.