A study of Eustachian tube measurements in infants and children is presented. The study included 33 Eustachian tubes from normal temporal bones and 10 Eustachian tubes from temporal bones harbouring acute otitis media. The temporal bones underwent histologic serial sectioning. The lumen of the Eustachian tube's first portion, i.e. the pharyngeal part, was measured with the aid of a grid mounted on a microscope. These measurements show: A. The Eustachian tube lumen grows and enlarges to a small extent with age. B. Each age group presents a considerable variation in the range of area of the lumen comparable with the natural biological distribution. C. No statistical difference was found between the size of the pharyngeal portion of the lumen of the Eustachian tube from temporal bones which had acute otitis media and those coming from non-pathological ears. This comparison took into consideration age and physiological distribution. These findings are similar to our earlier findings regarding the isthmic region.