Human chorionic gonadotropin bears structural homology to pituitary thyrotropin. The extremely elevated levels of human chorionic gonadotropin in patients with molar pregnancy or other trophoblastic diseases can lead to hyperthyroidism. We describe a patient with molar pregnancy who had secondary hyperthyroidism prepared rapidly by plasmapheresis for surgery. After first plasmapheresis the clinical picture improved dramatically. Three subsequent plasmapheresis provided a 75.1% decrease in serum free T3 concentrations and 63.9% free T4 concentrations and recovered after evacuation. This is the first using of the plasmapheresis in rapidly preparation of the patient who had secondary hyperthyroidism due to molar pregnancy.