There are many radiographies as routine work about which we have not fully studied by reason that it is rerative easy. Water position (for nase) is one of such a group. However if we knew perfectly true purpose of Water pasition, we could not make it light. The dignotic objects of radiograph by Water position are maxillary Sinus and Frontal sinus, and other supero anterior sinuses. In postero anterior projection, maxillary sinus over lap on the partes petrosa which has large x-ray absorption, this thing makes particular inclination of Water position for longitude direction of head necessary in radiography of maxillary sinus, on the other oner inclination brings image of maxillary sinus and part petrosa to o elaping imoge. We recognized true mean of Water position and secked suitable inclinational angle in Water position about Japanese.