Fiber is a notorious occupational hazard. Exposures to airborne asbestos fiber in the workplace increase the incidence of lung cancer for asbestos workers. Due to the lack of experimental data, the nature of fiber deposition in the human airway is unclear. In this study, a set of experiments were carried out to investigate the effect of fiber dimension and fiber inertia on the deposition pattern in the human airway replica. The deposition study was conducted by delivering aerosolized carbon fibers into the replica at constant inspiratory flow rates of 15-601/min. The results showed that impaction is the dominant deposition mechanism in this study. Most of the high-inertia fibers deposited in the oropharynx and the carina ridges of the bifurcations in tracheobronchial airways. A series of fiber deposition patterns were obtained and the deposition efficiencies were acquired for certain regions in the human airway replica. (C) 2006 Elsevier Ltd. All rights reserved.