α-fetoprotein (AFP), the foetal equivalent to albumin, is a 67 kDa glycoprotein produced during embryonic development and found in high concentrations in foetal serum and amniotic fluid. In normal nonpregnant adults, AFP is present in low concentrations in serum. However, AFP may be markedly increased in the serum from patients with cancer of the liver, testis or ovary. Quantitative determination of AFP in serum may be valuable in the management of patients with suspected or diagnosed liver cancer or germ cell tumors of the testis or ovary.