Ten patients with burn injuries (mean total body surface area burn = 29% ± 16%) were studied at various points in the course of their burn therapy. α1-Acid glycoprotein, albumin, and vancomycin concentrations were determined with either a trough or peak vancomycin quantitative determination. α1-Acid glycoprotein concentrations ranged from 125 to 333 mg/dl and albumin concentrations ranged from 1.7 to 4.2 gm/dl. Vancomycin protein binding, as determined by ultrafiltration, averaged 29% ± 6%. There was a strong (r = 0.92) relationship between percent protein-bound vancomycin and albumin. There was a poor statistical relationship between percent protein-bound vancomycin and α1-acid glycoprotein (r = 0.28). α1-Acid glycoprotein appeared to have virtually no effect on the protein-binding characteristics of vancomycin over the range of concentrations studied.