Written by a single author and authority in the field, The Clinical Marker hCG addresses several sensitive areas of clinical tests for the marker hCG: interpretation of results, different reference standards, application to pregnancy testing, early detection of hCG, differential of diagnosis of ectopic pregnancy, diagnostic potential in conjunction with ultrasound, use as a tumor marker, immunocytochemical applications, low-level hCG analysis, discordant results, and significance of subunits and their measurement. The evolution of hCG tests is thoroughly reviewed, with a clear description of the new generation immunoenzymetric tests and their advantages.