The relationship between the adequate endotracheal tube size, depth of tube fixation and incisor canina distance according to age(month) and body weight(kilogram) was studied in 148 infants. Intubation was proceeded by injection of thiopental sodium 4mg/kg and succinylcholine 1.5mg/kg in infants older than two months, whereas conscious intubation was used for infants less than two months of age. The relation coefficiency between tube size and body weight(0.83) was greater than that of age(0.76). The relation coefficiency between the depth of tube fixation and body weight(0.83) was greater than that of age(0.75) or tube size(0.77). The relation coefficiency between incisor carina distance and body weight(0.87) was greater than that of age(0.78) or tube size(0.80). Endobroncheal intubation was tried intentionally to evaluate the incidence of left broncheal intubation. Only one infant among 148 exhibited left broncheal intubation. This baby was full term, weighed 2.6kg with gastroschisis. With the above results we assume that body weight is the most important determinant factor for adequate tube size, depth of tube fixation and incisor carina distance. Attention should be paied to unintentional left broncheal intubation in infants less than one month old especially in low birth weight babies.