Human chorionic gonadotropin (hCG) stimulates testosterone production by the testicles. Because of the potential for abuse, hCG is banned (males only) in most sports and has been placed on the World Anti-Doping Agency list of prohibited substances. Intact hCG, free β-subunit (hCGβ), and β-subunit core fragment (hCGβcf) are the major variants or isoforms in urine. Immunoassays are used by antidoping laboratories to measure urinary hCG. Cross-reactivity with isoforms differs among immunoassays, resulting in widely varying results. We developed a sequential immunoextraction method with LC-MS/MS detection for quantification of intact hCG, hCGβ, and hCGβcf in urine.