Objective: (1) To test the hypothesis that there are no developmental changes in the pharyngeal airway depth and hyoid bone position from childhood to adulthood in normal Taiwanese persons, (2) to identify any sexual dimorphism, and (3) to find the predictive value of selective variables for the hyoid bone position. Materials and Methods: Lateral cephalometric radiographs of 239 normal Taiwanese (132 females and 107 males; aged 7-27 years) were separated into three stages according to dental age. Twenty-three linear and 20 angular measurements were made in all subjects. Sexual dimorphism was analyzed by Student's t-test. Analysis of variance was used to compare the three stages in both genders. A stepwise regression analysis was carried out to predict the hyoid bone position. The level of significance for all analyses was set at P Ͻ .05. Results:The pharyngeal airway depth increased from the mixed dentition stage to the permanent dentition stage in both genders. There was sexual dimorphism in the lower pharyngeal airway depth. The hyoid bone position showed an obvious difference in the permanent dentition stages between genders. The vertical position of the hyoid bone was associated with the mandibular morphology and position, but the relationship in males was reversed compared with that in females. Conclusions:The hypothesis was rejected. There are developmental changes in the pharyngeal airway depth and hyoid position from childhood to young adulthood. Sexual dimorphism appeared in the lower pharyngeal airway and the direction of change in the vertical position of the hyoid bone. (Angle Orthod. 2009;79:484-490.)