We managed two patients with secondary hyperthyroidism due to TSH secretion from pituitary adenomas using total intravenous anesthesia with propofol and fentanyl. Both propofol and fentanyl were infused with target-controlled infusion (TCI) systems. The anesthesiologists controlled the target concentration of propofol to maintain the bispectral index (BIS) in a range from 40 to 60, and the target concentration of fentanyl was kept within a range of 2.0 to 3.0 ng.ml-1. Propranolol was injected in 0.4 mg increments to a total dosage of 2.4 to 3.2 mg. Prostaglandin E1 (PGE1) was infused at a rate from 0.01 to 0.04 microgram.kg-1.min-1 to maintain a stable heart rate and stable systemic blood pressure. The anesthetic effects were excellent in both patients. The necessary concentration of propofol during anesthesia was 2.5 to 4.0 micrograms.ml-1, and the emergence concentration of propofol was 1.4 to 1.7 micrograms.ml-1. These values were almost equal to those obtained in patients without thyroid disease. In conclusion, we could maintain the anesthesia for the patients with hyperthyroidism safely and stably by titrating the concentration of propofol and fentanyl based on the BIS value, and by administrating propranolol and PGE1 to avoid hypertension and tachycardia.