The measurement of tracheal length in infants is difficult to perform in vivo. In adults, tracheal length may be consistent with age, but in infants, tracheal length may vary much more with age and other factors. This study used video rigid ventilation bronchoscopy to evaluate the length of the airway, concentrating on the population younger than 3 months old. There were 34 infants in this study: 14 boys and 20 girls. The mean length from the superior border of the vocal fold to the carina was 5.04 cm, and the mean tracheal length (from the ridge of the first tracheal ring to the carina) was 4.12 cm. There was no significant difference between boys and girls in the length from the vocal fold to the carina or in the tracheal length. The length from the vocal fold to the carina is best correlated to body weight, followed by body height and age.