Postoperative change of the frontal sinus cavity has not been well known. Fifty cases of the frontal sinuses were studied roentgenologically one year after operation which were performed by through the eye brow incision following T. Goto's method. The result were as follows: 1) Obliteration of the sinus cavities was seen in 50% of all cases. 2) In the large frontal sinuses, obliteration was not found, while in the small ones, obliteratin was seen in the majority of the cases. As for this reason

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... the author has pointed out potential energy of the sinus development, which is active in the well developed sinuses. 3) The forms of the frontal sinus, classified into three types according to the development in the frontal and ethmoidal bones, were related to the postoperative change of the cavity, e. g., the frontoethmoidal type shows difficulty of obliteration, while the frontal type shows less difficulty. The three types of the frontal sinus are as follows: The ethmoidal type has the cavity located in the ethmoidal bone. In fhe frontoethmoidal type the cavity is extended from the vertical plate of the frontal bone to the ethmoidal region. The frontal type is recognized generally as the typical sinus and its cavity is located in the vertical plate of the frontal bone, having the nasofrontal duct.