Circulating Nucleic Acids in Plasma/Serum III and Serum Proteomics (CNAPS) researchers report in this volume on the biology and clinical translation of circulating nucleic acids, a new and rapidly growing field that has continued to gain momentum over the last few years.In particular, tumor-derived DNA/RNA in the plasma/serum of cancer patients has shown promise for the diagnosis and prognosis of a variety of malignancies. In the field of prenatal diagnosis, the discovery of fetal DNA in maternal plasma has opened up new possibilities for noninvasive prenatal genetic analysis. Circulating nucleic acids have also been found in an increasing number of different cancer types and recently in noncancer-related pathologic conditions as well. Numerous questions still remain regarding the origin, release, clearance, clinical utility, and possible functionality of circulating nucleic acids. CNAPS III builds on the foundation of its successful predecessors. Serum proteomics is introduced as a new topic to CNAPS and is expected to provide yet another platform for breakthrough discoveries. Serum proteomics topics will address both cancer and early pregnancy.