: Human chorionic gonadotropin (hCG) is a polypeptide hormone studied as far as 1912, but researchers has no complete knowledge concerning its biological function. Since 1970' it is known that hCG can be found not only in the urine and serum of pregnant, but in choriocarcinoma and testicular cancer patients. Up-to-date one can distinguish four subtypes of hCG differing in secondary carbohydrate chains configuration as well as it regular and glycosylated forms, but non trophoblastic sources of this hormone, such as pituitary are still not widely known. The article gives an overlook on hCG studies in order to help clinicians in taking wise, evidence based decisions in asymptomatic patients with elevated hCG.