The purpose of this study was to determine the relationship between inflammation, increased alpha-1-acid glycoprotein (AAG), and lidocaine tolerance during fiber-optic bronchoscopy. Previous studies indicate that serum lidocaine levels vary widely from one individual to another. One reason for these variations may be the presence of an ongoing inflammatory process, which enhances serum AAG, a major binding protein of lidocaine. To test this hypothesis, we assayed free and bound lidocaine as well as AAG in the blood of 12 patients after administration of 9 mg/kg of lidocaine during fiber-optic bronchoscopy. Some of the subjects had clear evidence of inflammation or infection. A correlation was found between AAG and total and bound lidocaine but not between AAG and free lidocaine (which remained almost constant). Thus, in spite of the high total levels of lidocaine observed in some patients with inflammatory processes, the free fraction (which is the active and toxic fraction) remained low.