Biomarkers could be critical and useful tools for assessing the biological effects of smoking and detecting differences between potentially reduced exposure product (PREP) and conventional cigarettes. Smoking-related biomarkers can be classified into three categories as biomarkers of exposure, biomarkers of effects, and biomarkers of potential harm. When compared with the biomarkers of effects or harm, the biomarkers of exposure for chemical constituents of cigarette smoke are well established and characterized. In addition, they could offer the important information in understanding how cigarette smoke interacts with biological molecules and causes the disease to human. Therefore, we provide an overview of 6 biomarkers of exposure (Nicotine and nicotine metabolites, Carboxyhaemoglobin, NNAL (4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanol) and NNAL - glucuronide, 3-Hydroxypropyl-mercapturic acid, and Monohydroxy-butenyl-mercapturic acids, and Urine mutagenicity) which were validated through extensive research and clinical experience. These reliable biomarkers could help identify the efficacy of PREP by predicting early toxicological effects and lead to improve it.