Biological markers are material measures obtained from the bodies or excretions of individuals potentially usable to detect: environmental exposures effects of exposures. The rationale for biological markers in epidemiologic research is strong in that markers have the potential for improving the accuracy of our "exposure variables" permitting the identification of preclinical disease and providing opportunities for prevention allowing for more homogeneous and etiologically relevant classifications of disease and enhancing our understanding of the biological processes leading to disease occurrence. When we are dealing with biomarkers they need validation using laboratory epidemiologic and clinical studies. The analytic validity clinical validity and clinical utility of a biomarker are important for evaluating it. The use of biomarkers in epidemiologic research raises a number of ethical legal and social issues. Biomarkers in reproduction epidemiology are considered as markers of events before and around fertilization biological markers in discovering or interpreting female reproductive disorders that might be owed to environmental causes markers of the pre- and peri-implantation phases and markers of the postimplantation phase experience with studies of chromosome anomaly in spontaneous abortion.