The pharmacokinetic characteristics of desflurane, isoflurane and sevoflurane (16 patients for each anaesthetic) were estimated from measurements of inspired and end-expired agent concentrations and ventilation, obtained during routine anaesthesia in patients undergoing maxillofacial surgery (mean age 38 yr, duration of anaesthesia approximately 2 h). A two-compartment model described the data adequately. Although isoflurane and sevoflurane have almost the same tissue/blood partition coefficients, significant differences between substances were observed for the peripheral volume of distribution (medians and ranges: desflurane, 612 (343-1850) mlvapour kgbw-1; isoflurane, 4112 (1472-9396) mlvapour kgbw-1; sevoflurane, 1634 (762-8843) mlvapour kgbw-1) and the transport clearance from the central to the peripheral compartment (desflurane, 7.0 (4.4-11.1) mlvapour kgbw-1 min-1; isoflurane, 30.7 (15.9-38.7) mlvapour kgbw-1 min-1; sevoflurane, 13.0 (9.8-22.4) mlvapour kgbw-1 min-1). Thus, during clinical anaesthesia the important characteristics of the compounds could be obtained and compared between substances from simple data.