High-resolution capillary gas chromatography-mass spectrometry with selective ion monitoring and using deuterated 3-tert-butyl-4-hydroxyanisole (BHA) as an internal standard was used to measure BHA in the plasma and urine of human volunteers after oral administration of 30 or 5 mg of the compound in olive oil. Pharmacokinetic studies showed similar plasma-concentration profiles in subjects treated with either level of BHA. About 20% of the administered dose was excreted as BHA glucuronide in the urine within the first 24 hr.