The lumen of the eustachian tube in foetuses, neonates and infants was demonstrated in cadaver temporal bones immediately after death by air and contrast medium using high-resolution computed tomography with axial and coronal projections. Special consideration was given to the deviation of the tube from the sagittal and horizontal plane and the functional unit consisting of the processes of tensor palatini muscle. At this stage of development the lumen of the cartilaginous portion shows a constant almost circular form, quite unlike the shape in adults. A well developed isthmus between the bony and cartilaginous part is absent. In a 6-month-old foetus the tube is horizontal to the base of the skull, whereas in a 6-month-old infant it forms an angle of approximately 10 degrees. The angle to the sagittal plane changes in the same period from approximately 37 degrees to 40 degrees. In a 6-month-old foetus the fibres of the tensor palatini muscle also run in an almost horizontal line because of the tiny processus pterygoideus and are forced into a steeper direction as a result of its gradual growth. As there is almost no fulcrum function, a tubal opening effect or mechanism of the muscle fibres at this stage of development seems extremely doubtful.